chapter 4 elements and symbols - pbworkschemistry121.pbworks.com/w/file/fetch/101481166/ch4...

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C. Timberlake

© 2016 Pearson Education, Inc.

Karen C. Timberlake

Lecture Presentation

Chapter 4

Elements and

Symbols


Karen C. Timberlake


Chapter 4 Atoms and Elements

In addition to growing

crops and raising

animals, farmers must

understand how to

perform chemical tests

and how to apply

fertilizers and pesticides

or herbicides to crops.


Karen C. Timberlake


Chapter 4 Readiness

Key Math Skills

• Using Positive and Negative Numbers in Calculations (1.4B)

• Calculating Percentages (1.4C)

• Rounding Off (2.3)

Core Chemistry Skills

• Counting Significant Figures (2.2)

• Using Significant Figures in Calculations (2.3)


Karen C. Timberlake


4.1 Elements and Symbols

Elements

• are pure substances

from which all other

things are built.

• cannot be broken

down into simpler

substances.

• are listed on the inside

front cover of this text.

Learning Goal Given the name of an element, write its

correct symbol; from the symbol, write the correct name.


Karen C. Timberlake


Some Elements and Their Names

Element names come from planets, mythological figures,

minerals, colors, geographic locations, and famous people.


Karen C. Timberlake


Chemical Symbols

Chemical symbols

• represent the names of the

elements.

• consist of one to two letters

and start with a capital letter.

One-Letter Symbols Two-Letter Symbols

C carbon Co cobalt

N nitrogen Ca calcium

F fluorine Al aluminum O oxygen Mg magnesium


Karen C. Timberlake


Names and Symbols of Common Elements


Karen C. Timberlake


Chemical Symbols from Latin Names

Ag silver (argentum)

Au gold (aurum)


Karen C. Timberlake


Study Check

Write the correct chemical symbols for each of the following

elements:

A. iodine

B. iron

C. magnesium

D. zinc

E. nitrogen


Karen C. Timberlake


Study Check

Give the names of the elements with the following symbols:

A. P

B. Al

C. Mn

D. H

E. K


Karen C. Timberlake


Chemistry Link to Health: Toxicity of Mercury

Mercury (Hg)

• is a silvery, shiny element that is a liquid at room

temperature.

• can enter the body by mercury vapor inhalation, contact

with the skin, or ingestion of water or food contaminated

with mercury.

Once mercury has entered the body, it destroys proteins and

disrupts cell function. Long-term exposure can

• damage the brain and kidneys.

• cause mental retardation.

• decrease physical development.


Karen C. Timberlake


Chemistry Link to Health: Toxicity of Mercury

Mercury contamination comes from

• industrial wastes.

• fish and seafood.

• batteries.

• compact fluorescent bulbs.


Karen C. Timberlake


4.2 The Periodic Table

The periodic table

organizes 118

elements into groups

with similar properties

and places them in

order of increasing

atomic mass.

Learning Goal Use the periodic table to identify the group

and the period of an element; identify the element as a

metal, a nonmetal, or a metalloid.


Karen C. Timberlake


Periodic Table of Elements

• First proposed by Russian Chemist Dmitiri Mendeleev in 1869• Organized the known elements by similarities in physical and

chemical properties and then my increasing atomic “weights,” as they were know back then. Today, we call it atomic mass

• Since 1915, the elements have been arranged by increasing atomic number


Karen C. Timberlake


Periodic Table of Elements


Karen C. Timberlake


Groups and Periods

In the periodic table,

• elements are arranged according to properties.

• groups contain elements with similar properties in

vertical columns.

• periods are horizontal rows of elements, counted

from top to bottom of the table as Periods 1−7.


Karen C. Timberlake


Groups and Periods

Vertical columns represent groups of elements, and horizontal

rows represent periods.


Karen C. Timberlake


Group Numbers

Group numbers are written at the top of each vertical column.

• Use the letter A for representative elements

(Groups 1A–8A).

• Use the letter B for transition elements (Groups 3B–12B).

An alternative system uses numbers of 1–18 for all of the

groups, from left to right, across the periodic table.

Because both systems are currently in use, they are both

shown on the periodic table in this text and are included in our

discussions of elements and group numbers.


Karen C. Timberlake


Group Names – some groups have common names


Karen C. Timberlake


Alkali Metals

Group 1A (1), the alkali

metals, includes the

following:

• lithium (Li)

• sodium (Na)

• potassium (K)

• rubidium (Rb)

• cesium (Cs)


Karen C. Timberlake


Alkaline Earth Metals

Group 2A (2) elements, the alkaline

earth metals, are shiny but not as

reactive as Group 1A metals. They

include the following:

• beryllium (Be)

• magnesium (Mg)

• calcium (Ca)

• strontium (Sr)

• barium (Ba)

• radium (Ra)

Strontium gives the red color in fireworks.


Karen C. Timberlake


Halogens

Group 7A (17), the

halogens, includes the

following:

• fluorine (F)

• chlorine (Cl)

• bromine (Br)

• iodine (I)

© 2013 Pearson Education, Inc. Chapter 3, Section 2

Noble Gases

Group 8A (18) is the noble gases, which include helium

(He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe)

and radon (Ra).

Noble gas elements are extremely unreactive (i.e. they

are seldom found in combination with other elements).

Were not discovered until the 1890s because of their

inactivity, so they were not on Mendeleev’s original

table

23


Karen C. Timberlake


Study Check

Identify the element described by each of the following groups

and periods:

1. Group 7A (17), Period 4

A. Br B. Cl C. Mn


A. beryllium B. boron C. magnesium


A. phosphorus B. arsenic C. nitrogen


Karen C. Timberlake


3 Categories of Elements: Metals,

Nonmetals, and Metalloids

The heavy zigzag line separates metals and nonmetals.

• Metals are located to the left.

• Nonmetals are located to the right.

• Metalloids are located along the heavy zigzag line.


Karen C. Timberlake


Characteristics of Metals, Nonmetals, and

Metalloids

Metals, except for hydrogen, located

on the left of the periodic table,

• are shiny and ductile, and conduct

heat and electricity.

• are solids, except for mercury

(Hg), which is a liquid.

Nonmetals, located on the right side

of the periodic table,

• are dull, brittle, and poor

conductors but often good

insulators.

• have low densities and melting

points.


Karen C. Timberlake


Characteristics of Metals, Nonmetals, and

Metalloids

Metalloids, located along the heavy zigzag line on the

periodic table,

• exhibit properties of metals and nonmetals.

• are better conductors than nonmetals but not as

good as metals.

• are used as semiconductors and insulators,

because they can be modified to function as

conductors or insulators.


Karen C. Timberlake


Comparing a Metal, a Nonmetal, and a

Metalloid


Karen C. Timberlake


Study Check

Identify each of the following elements as a metal,

a nonmetal, or a metalloid:

A. sodium

B. chlorine

C. silicon

D. iron

E. carbon


Karen C. Timberlake


Study Check

List all of the elements that match the description.

A. metals in Group 4A (14)

Sn, Pb, C, Si, Ge

B. nonmetals in Group 5A (15)

Bi, N, P, As, Sb

C. metalloids in Group 4A (14)

C, Si, Ge, Sn, Pb


Karen C. Timberlake


An atom is the smallest

particle of an element that

retains the characteristics

of that element.

Aluminum foil contains

atoms of aluminum.

Learning Goal Describe the electrical charge and location in

an atom for a proton, a neutron, and an electron.

4.3 The Atom – A Brief History of Atomic Theory


John Dalton’s Atomic Theory ( circa 1808)

32

Dalton theorized that Atoms

are tiny particles of matter too small to see,

are able to combine with other atoms to make compounds, and

are similar to each other for each element and different from atoms of other elements.

A chemical reaction is the rearrangement of atoms.

Atoms are never created or destroyed during chemical and physical changes

Dalton envisioned

atoms to be solid,

indivisible spheres, like

billiard balls called the

“billiard ball model”


Atomic Theory in the late 1890’s

Discovery of radioactivity and the discovery of

the first subatomic particle (the electron)

meant Dalton’s solid sphere model had to

change.

JJ Thomson, discoverer of the electron,

developed “plum pudding model.”

Electron was tiny (1/2000th the size of the

atom), negatively charged particle

As atom electrically neutral, electron must be

embedded in “positive dough” of atom like

plums in plum pudding33


Karen C. Timberlake


Atoms contain the following

subatomic particles:

• protons that have a positive

(+) charge

• electrons that have a negative

(–) charge

• neutrons that have no charge

(neutral)

Like charges repel and unlike charges

attract.

Electrical Charges in an Atom


Karen C. Timberlake


From his experiment, J. J. Thomson realized that

• cathode rays contain negatively charged particles.

• particles (now called electrons) have a much smaller mass

than the atom.

Thomson proposed a “plum-pudding” model of the atom in

which protons and electrons were randomly distributed in a

positively charged cloud, like plums in a pudding.

J. J. Thomson’s Cathode Ray Tube Exp


Karen C. Timberlake


J. J. Thomson’s Plum Pudding Model (1897)

Thomson’s “plum-pudding” model had protons

and electrons scattered throughout the atom.


Karen C. Timberlake


In Rutherford’s gold foil experiment, positively charged

particles

• were aimed at atoms of gold.

• mostly went straight through the atoms.

• were deflected only occasionally.

Rutherford’s experiment concluded that there must be a small, dense, positively charged nucleus in the atom that deflects positive particles that come close.

Rutherford’s Gold Foil Experiment (1911)


Karen C. Timberlake


Rutherford’s Gold Foil Experiment

(a) Positive particles are aimed at a piece of gold foil. (b) Particles that

come close to the atomic nuclei are deflected from their straight path.


Rutherford’s Nuclear Model of the

Atom (1911)

The atom is mostly empty space

All of the positive charge is located in a tiny,

dense nucleus

The negative electrons are located at a

distance away and must be constantly

moving to avoid being pulled into the nucleus

39


Discovery of Proton and Neutron

Positive charge comes in nucleus actually

due to a particle, called the proton

(Rutherford, 1919)

More mass in the nucleus than protons could

account for in 1932, an electrically neutral

particle called the “neutron” was discovered

by James Chadwick.

40


Karen C. Timberlake


An atom consists of

• a nucleus, located in the center of the atom, that

contains protons and neutrons and represents most of

the mass of an atom.

• electrons that occupy a large, empty space around the

nucleus.

Structure of the Atom


Karen C. Timberlake


Structure of the Atom

In an atom, the protons and neutrons that make up almost all the mass are

packed into the tiny volume of the nucleus. The rapidly moving electrons

(negative charge) surround the nucleus and account for the large volume

of the atom.


Karen C. Timberlake


Because the mass of subatomic particles is so small,

• chemists use a very small unit of mass called the atomic

mass unit (amu).

• 1 amu has a mass equal to 1/12 of the mass of the

carbon-12 atom that contains six protons and six neutrons.

• 1 amu = 1 Dalton (Da) in biology.

• Electrons have such a small mass that they are not

included in the mass of an atom.

Mass of the Atom


Karen C. Timberlake


Subatomic particles have a very small mass, and an

electron has a mass that is much less than that of a

proton or a neutron.

Subatomic Particles in the Atom


Karen C. Timberlake


Which of the following subatomic particles fits each of the

descriptions below?

protons, neutrons, or electrons

A. found outside the nucleus

B. have a positive charge

C. have mass but no charge

Study Check


Karen C. Timberlake


4.4 Atomic Number and Mass Number

All atoms of an element

have the same number

of protons and the

same atomic number.

Learning Goal Given the atomic number and the mass

number of an atom, state the number of protons, neutrons,

and electrons.


Karen C. Timberlake


Atomic Number

The atomic number

• is a whole number specific for each element.

• is the same for all atoms of an element.

• is equal to the number of protons in an atom.

• appears above the symbol of an element in the

periodic table.

11

Na

Atomic number

Symbol


Karen C. Timberlake


Atomic Number = Protons in an Atom

Atomic number = number of protons—for example,

• the atomic number of H is 1; every H atom has one proton.

• the atomic number of C is 6; every C atom has six protons.

• the atomic number of Cu is 29; every Cu atom has 29 protons.

Core Chemistry Skill Counting Protons and Neutrons


Karen C. Timberlake


Atomic Number = Protons in an Atom

All atoms of lithium (left) contain three protons, and all atoms of carbon (right) contain six protons.


Karen C. Timberlake


Atoms are Neutral

For neutral atoms, the net charge is zero.

number of protons = number of electrons

Aluminum has 13 protons and 13 electrons. The net (overall)

charge is zero.

13 protons (13+) + 13 electrons (13–) = 0


Karen C. Timberlake


Study Check

Use the periodic table to fill in the atomic number, number of protons, and number of electrons for each of the following elements:

Element Atomic

Number

Protons Electrons

N

Zn

S


Karen C. Timberlake


Mass Number

The mass number

• represents the number of particles in the nucleus.

• is equal to the number of protons + the number of neutrons.

• is always a whole number.

• does not appear in the periodic table.


Karen C. Timberlake


Composition of Some Atoms of Different

Elements


Karen C. Timberlake


Study Tips: Protons and Neutrons

Number of protons = atomic number

Number of protons + neutrons = mass number

Number of neutrons = mass number – atomic number

Note: Mass numbers are given for specific isotopes only.


Karen C. Timberlake


Study Check

An atom of lead (Pb) has a mass number of 207.

A. How many protons are in the nucleus?

B. How many neutrons are in the nucleus?

C. How many electrons are in the atom?


Karen C. Timberlake


4.5 Isotopes and Atomic Mass

The atomic symbol for

an isotope of magnesium

with 12 neutrons.

Learning Goal Determine the number of protons, electrons,

and neutrons in one or more of the isotopes of an element;

calculate the atomic mass of an element using the percent

abundance and mass of its naturally occurring isotopes.

12

24 Mg


Karen C. Timberlake


Isotopes

Isotopes

• are atoms of the same element.

• have different mass numbers.

• have the same number of protons but different numbers

of neutrons.

• can be distinguished by their atomic symbols.

Core Chemistry Skill Writing Atomic Symbols for Isotopes


Karen C. Timberlake


Atomic Symbols: Subatomic Particles

Given the atomic symbols, determine the number of protons,

neutrons, and electrons.

8

16 O 15

31P 30

65 Zn

ANALYZE Atomic Mass Number of

THE PROBLEM Number Number Protons

number in number in equal to

lower left upper left atomic

corner corner number


Karen C. Timberlake


Atomic Symbols: Subatomic Particles

Determine the number of protons, neutrons, and electrons.

8

16 O

Isotope Atomic

Number

Mass

Number

Number of

Protons

Number of

Neutrons

8 16 8 8 (16–8)

15 31 15 16 (31–16)

30 65 30 35 (65–30)

8

16 O

15

31P

30

65 Zn


Karen C. Timberlake


Isotopes of Magnesium

Magnesium, with three

naturally occurring

isotopes, has an atomic

mass of 24.31 amu.


Karen C. Timberlake


Isotopes of Magnesium


Karen C. Timberlake


Study Check

Naturally occurring carbon consists of three isotopes: 12C, 13C, and 14C. State the number of protons, neutrons, and

electrons in each of the three isotopes.


Karen C. Timberlake


Study Check

Write the atomic symbols for atoms with the following

subatomic particles:

A. 8 protons 8 neutrons 8 electrons

B. 17 protons 20 neutrons 17 electrons

C. 47 protons 60 neutrons 47 electrons


Karen C. Timberlake


Study Check

1. Which of the pairs below are isotopes of the same

element?

2. In which of the pairs below do both atoms have eight

neutrons?

A.

B.

C.

8

15 X

7

15 X

6

12 X

6

14 X

7

15 X

8

16 X


Karen C. Timberlake


Calculating Average Atomic Mass

Atomic mass is the

• weighted average of all

naturally occurring

isotopes of that element.

• number on the periodic

table below the chemical

symbol.

Chlorine, with two naturally

occurring isotopes, has an

atomic mass of 35.45 amu.


Karen C. Timberlake



To calculate atomic mass,

• use the experimental percent abundance of each isotope of

the element.

• multiply the percent abundance by the atomic mass of that

isotope.

• sum the total mass of all isotopes.


Karen C. Timberlake



To calculate atomic mass of chlorine, use experimental data

for both isotopes.

Atomic mass of Mg = 18.88 amu + 2.531 amu + 2.902 amu

= 24.31 amu (weighted average mass)


Karen C. Timberlake


Average Atomic Masses of Some Elements


Karen C. Timberlake


Study Check

Lithium consists of two naturally occurring isotopes, 6Li and 7Li. Use the periodic table to predict which isotope is the

more prevalent one. (According to the periodic table, the

atomic mass of lithium is 6.941 amu.)


Karen C. Timberlake


Study Check

Gallium is an element found in lasers used in compact disc

players. In a sample of gallium, there is

60.10% of 69Ga (atomic mass 68.926) atoms

39.90% of 71Ga (atomic mass 70.925) atoms

What is the atomic mass of gallium?


Karen C. Timberlake


4.6 Electron Energy Levels

A rainbow forms when

light passes through

water droplets.

Learning Goal Describe the energy levels, sublevels, and

orbitals for the electrons in an atom.


Karen C. Timberlake


Electromagnetic Radiation

We experience electromagnetic radiation in different forms,

such as light, the colors of a rainbow, or X-rays.

Electromagnetic radiation consists of energy particles that

move as waves of energy.

• The distance between the peaks of waves is called the

wavelength.

• High-energy radiation has shorter wavelengths.

• Low-energy radiation has longer wavelengths.


Karen C. Timberlake


Atomic Spectrum

When light from a heated element passes through a

prism, it separates into distinct lines of color separated

by dark areas called an atomic spectrum.

Each element has its own unique atomic spectrum.

In an atomic spectrum, light from a heated element separates into distinct lines.


The Bohr Model (1913)

Proposed by Danish physicist Niels Bohr

Problems with Rutherford’s model as

conflicted with laws of physics

Bohr proposed new laws were needed for tiny

particles like electrons led to development

of quantum physics

Bohr’s model solved some of these problems

Main ideas electrons can only have certain

allowable energies, which correspond to

different distances from the nucleus = Energy

Levels74



Energy levels radiate away from nucleus

Energy levels are labeled by what is called

the principal quantum number “n”

Each holds a distinct number of electrons

which corresponds to 2n2

n = 1 holds 2(1)2 = 2 electrons



75


Karen C. Timberlake


Electron Energy Levels

The lines in an atomic spectrum are associated with the

changes in energies of the electrons.

In an atom, each electron has a specific energy, known as its

energy level, which

• is assigned principal quantum numbers (n) = (n = 1,

n = 2, …).

• increases in energy as the value of n increases and

electrons are farther away from the nucleus.

The energy of an electron is quantized—electrons can have

only specific energy values.


Karen C. Timberlake


Electromagnetic Spectrum

The electromagnetic spectrum shows the arrangement of

wavelengths of electromagnetic radiation, with the visible range

from 700 to 400 nm.


Karen C. Timberlake


Electrons and Energy Levels

• Electrons with the same

energy are grouped in the

same energy level.

• Energy levels are assigned

values called principal

quantum numbers (n),

(n = 1, n = 2, …).

An electron can have only the

energy of one of the energy

levels in an atom.


Karen C. Timberlake


Changes in Electron Energy Level

• Electrons move to a

higher energy level

when they absorb

energy.

• When electrons fall

back to a lower energy

level, light is emitted.

• The energy emitted or

absorbed is equal to

the differences

between the two

energy levels.



80

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=hVrrHEVcCjcgLM&tbnid=wT2l7qDHFKnRvM:&ved=0CAUQjRw&url=http%3A%2F%2Fperfume.hosterbox.net%2F22%2Fbohr-electron-shell&ei=vKpkUfLCMozYigKQj4HIBw&bvm=bv.44990110,d.cGE&psig=AFQjCNEN7Pz1n9M2I2N-QIT9TBDWZPabmA&ust=1365638131154517

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=hVrrHEVcCjcgLM&tbnid=wT2l7qDHFKnRvM:&ved=0CAUQjRw&url=http%3A%2F%2Fperfume.hosterbox.net%2F22%2Fbohr-electron-shell&ei=vKpkUfLCMozYigKQj4HIBw&bvm=bv.44990110,d.cGE&psig=AFQjCNEN7Pz1n9M2I2N-QIT9TBDWZPabmA&ust=1365638131154517


Problem with Bohr Model

Only worked for H atom

Historically important model because:

it was the first to say different laws of physics

needed led to development of quantum

theory, or quantum physics

It was the first to suggest that electrons can

only have certain, allowable energies (energy

of the electron is quantized)

Still use energy levels today

81


Modern Atomic Theory Based on Quantum Physics (developed in the

1920s)

Treats the electron as both a particle and a

standing wave (yikes!, what does that mean?)

the electron can have only certain allowable

energies (e- energy is quantized) which

correspond to different distances from the

nucleus = energy levels

Solutions to the math equations of quantum

physics provide the most probable region

around the nucleus of finding an electron.

These “probability regions” are also known as

orbitals82


Modern Model of the Atom

83

Called electron cloud model

Today, we can see the surfaces of atoms

Device used is based on the wave properties of electrons (electron microscopes based on the wave properties of electrons, have very tiny wavelength, so can see very tiny things)

Images of nickel atoms

are produced when nickel is magnified

millions of times by a scanning

tunneling microscope (STM). This

instrument generates an image of

the atomic structure.


84

Models of the Atom Between 1808 and Now


Karen C. Timberlake


Energy Sublevels and The Quantum Mechanical Model

The result of the quantum mechanical model (a

mathematical model) is that energy levels are split into

sublevels.

It is the arrangement of electrons that determines the

physical and chemical properties of an element.

• Each energy level consists of one or more sublevels.

• The number of sublevels in an energy level is equal to the

principal quantum number n of that energy level.

• The sublevels are identified as s, p, d, and f.

• The order of sublevels in an energy level is

s < p < d < f


Karen C. Timberlake


Sublevels


Karen C. Timberlake


The location of an electron

is described in terms of

probability.

• Orbitals are a three-

dimensional volume in

which electrons have the

highest probability of

being found.

• The s orbitals are shown

as spheres.

s Orbitals

(a) The electron cloud of an s orbital

represents the highest probability of

finding an s electron. (b) The s orbitals

are shown as spheres. The sizes of the

s orbitals increase because they contain

electrons at higher energy levels.


Karen C. Timberlake


p Orbitals

There are three p orbitals,

starting with n = 2.

• Each p orbital has two

lobes, like a balloon tied

in the middle, and can

hold a maximum of two

electrons.

• The three p orbitals are

arranged perpendicular to

each other along the x, y,

and z axes around the

nucleus.


Karen C. Timberlake


p Orbitals

A p orbital has two regions of high probability, which gives a “dumbbell” shape. (a)

Each p orbital is aligned along a different axis from the other p orbitals. (b) All three p

orbitals are shown around the nucleus.


Karen C. Timberlake


d Orbitals

Each of the d sublevels contains five d orbitals.

Four of the five d

orbitals consist of four

lobes that are aligned

along or between

different axes. One d

orbital consists of two

lobes and a doughnut-

shaped ring around its

center.


Karen C. Timberlake


Orbital Capacity and Electron Spin

The Pauli exclusion principle states that

• each orbital can hold a maximum of two electrons.

• electrons in the same orbital repel each other.

• electrons in the same orbital must have their magnetic spins

cancel (they must spin in opposite directions).

We can represent magnetic spins with an arrow

An orbital can hold up

to two electrons with

opposite spins.


Karen C. Timberlake


Number of Electrons in Sublevels

There is a maximum number of electrons that can fill each

sublevel.

• Each s sublevel has one orbital and can hold a maximum

of two electrons.

• Each p sublevel has three orbitals and can hold a

maximum of six electrons.

• Each d sublevel has five orbitals and can hold a maximum

of 10 electrons.

• Each f sublevel can has 7 orbitals and can hold a

maximum of 14 electrons.


Karen C. Timberlake


Number of Electrons in Sublevels


Karen C. Timberlake


Study Check

Which of the following elements are likely to have electrons

in the 3p sublevel?

C

Si

O

As


Karen C. Timberlake


4.7 Electron Configurations

Electron configurations follow the order of occupied sublevels

on the periodic table.

Learning Goal Draw the orbital diagram and write the

electron configuration for an element.


Karen C. Timberlake


Orbital Diagrams

Orbital diagrams use boxes to show how electrons

• are arranged in the orbitals of an atom.

• fill the orbitals and energy levels from lowest to highest

energy level.

• fill orbitals within the same sublevel one at a time, before

pairing the electrons.


Karen C. Timberlake


Electron Configurations

Chemists use a notation called electron configuration to

• indicate the placement of electrons in an atom.

• show how electrons fill energy levels and sublevels in order

of increasing energy.

• write an abbreviated form using a noble gas to represent all

electrons preceding it.

Core Chemistry Skill Writing Electron Configurations

Electron Configuration for Carbon


Karen C. Timberlake


Period 1: Hydrogen and Helium


Karen C. Timberlake


Period 2: Lithium to Neon


Karen C. Timberlake


Guide to Drawing Orbital Diagrams


Karen C. Timberlake


Drawing Orbital Diagrams

Nitrogen atoms are found in amino acids, proteins, and

nucleic acids. Draw the orbital diagram for nitrogen.

STEP 1 Draw boxes to represent the occupied

orbitals.

Nitrogen’s atomic number is 7, which means it has seven

electrons. For the orbital diagram, we draw boxes to

represent the 1s, 2s, and 2p orbitals.


Karen C. Timberlake





STEP 2 Place a pair of electrons with opposite spins

in each filled orbital.

First we place a pair of electrons with opposite

spins in the1s and 2s orbitals.


Karen C. Timberlake





STEP 3 Place the remaining electrons in the last

occupied sublevel in separate orbitals.

Place three remaining electrons in the three

separate 2p orbitals, with arrows drawn in the

same direction.


Karen C. Timberlake


Period 3: Sodium to Argon

Electron Configurations and the

Periodic Table

The electron configurations of elements are related to their

positions on the periodic table. Different sections or blocks

correspond to sublevels s, p, d, and f.


Karen C. Timberlake



Karen C. Timberlake


Blocks on the Periodic Table

1. The s block contains elements in Groups 1A (1) and 2A

(2). This means the final one or two electrons are in the s

sublevel.

2. The p block consists of elements in Group 3A (13) to

Group 8A (18). There are six p block elements in each

period, because three p orbitals can hold a maximum of six

electrons.

3. The d block, which contains transition elements, first

appears after calcium (atomic number 20). There are

10 elements in the d block, because five d orbitals can hold

a maximum of 10 electrons.


Karen C. Timberlake


Blocks on the Periodic Table

4. The f block, the inner transition elements, is the two rows

of elements at the bottom of the periodic table. There are

14 elements in each f block, because seven f orbitals can

hold a maximum of 14 electrons.

Core Chemistry Skill Using the Periodic Table to Write

Electron Configurations

Guide to Writing Configurations Using

Sublevel Blocks

Use the sublevel blocks on the periodic table to write the electron

configuration for chlorine.

STEP 1 Locate the element on the periodic table.

Chlorine (atomic number 17) is in Group 7A (17)

and Period 3.

STEP 2 Write the filled sublevels in order, going across

each period.


Karen C. Timberlake


Guide to Writing Configurations Using

Sublevel Blocks

Use the sublevel blocks on the periodic table to write the

electron configuration for chlorine.

STEP 3 Complete the configuration by counting the

electrons in the last occupied sublevel block.

Because chlorine is the fifth element in the 3p

block, there are five electrons in the 3p sublevel.

The electron configuration for chlorine (Cl) is

1s22s22p63s23p5.


Karen C. Timberlake


Electron Configurations: Period 4 and

Above

Beginning in Period 4,

• the 4s sublevel fills before the 3d sublevel, because the 3d

sublevel is slightly lower in energy than the 4s sublevel.

• the 5s sublevel fills before the 4d sublevel.

• the 6s sublevel fills before the 5d sublevel.


Karen C. Timberlake


Electron Configurations: Period 4 and

Above


Karen C. Timberlake



Karen C. Timberlake


Study Check


electron configuration for selenium.


Karen C. Timberlake


Solution




Selenium is in Period 4, Group 6A (16).


each period.


Karen C. Timberlake


Solution





Because selenium is the fourth element in the 4p

block, there are four electrons to place in the 4p

sublevel.

The electron configuration for selenium (Se) is

1s22s22p63s23p64s23d104p4.


Karen C. Timberlake


3d Sublevel Exceptions

• For chromium (Cr), moving one of the 4s electrons to the

3d sublevel adds stability with a half-filled d subshell, and

the resulting configuration is 4s13d5.

• For copper (Cu), moving one of the 4s electrons to the 3d

sublevel adds stability with a filled d subshell, and the

resulting configuration is 4s13d10.


Karen C. Timberlake


Study Check

Use the periodic table to give the symbol and name for the

element with the electron configuration of

1s22s22p63s23p64s23d7.


Karen C. Timberlake


Solution

Use the periodic table to give the symbol and name for the

element with the electron configuration of

1s22s22p63s23p64s23d7.

There are seven electrons in the 3d sublevel. Thus, the

element is cobalt (Co).

Sc Ti V Cr Mn Fe Co Ni Cu Zn

1 2 3 4 5 6 7


Karen C. Timberlake


Study Check

Write the electron arrangement for the following elements:

C

Si

O


Karen C. Timberlake


Solution


C: atomic number 6, Period 2, Group 4A (14)

Si: atomic number 14, Period 3, Group 5A (15)

O: atomic number 8, Period 2, Group 6A (16)


Karen C. Timberlake


Solution


each period.

C 1s22s2

Si 1s22s22p63s2

O 1s22s2


Karen C. Timberlake


Solution



C, the second element in the 2p block, has two

electrons to place in the 2p sublevel: 1s22s22p2.

Si, the second element in the 3p block, has two

electrons to place in the 3p sublevel:

1s22s22p63s23p2.

O, the fourth element in the 2p block, has four

electrons to place in the 2p sublevel: 1s22s22p4.


Karen C. Timberlake


4.8 Trends in Periodic Properties

The atomic size of representative elements is affected by the

attractive forces between the protons in the nucleus and the

electrons in the outermost energy level.

Learning Goal Use the electron configurations of elements

to explain the trends in periodic properties.


Karen C. Timberlake


Group Numbers: Valence Electrons

• For representative elements in Groups 1A (1)–8A (18),

chemical properties are due to the number of valence

electrons.

• Valence electrons are the number of electrons in the

outermost energy level.

• The group number gives the number of valence electrons

for the representative elements.

Core Chemistry Skill Identifying Trends in Periodic

Properties


Karen C. Timberlake


Valence Electron Configurations

Valence Electron Configuration for Representative Elements

in Periods 1 to 4


Karen C. Timberlake


Study Check

Using the periodic table, write the group number, the period,

and the valence electron configuration for the following:

A. calcium

B. lead


Karen C. Timberlake


Solution

The valence electrons are the outermost s and p electrons.

Although they may have electrons in the d or f sublevel, they

are not valence electrons.

A. Calcium is in Group 2A (2), Period 4. It has a valence

electron configuration of 4s2.

B. Lead is in Group 4A (14), Period 6. It has a valence

electron configuration of 6s26p2.


Karen C. Timberlake


Lewis Symbols

Lewis symbols represent the valence electrons as dots

placed on sides of the symbol for an element.

• One to four valence electrons are arranged as single dots.

• Five to eight valence electrons are arranged with at least

one pair of electrons around the symbol for the element.

Core Chemistry Skill Drawing Lewis Symbols

Lewis Symbols for Magnesium


Karen C. Timberlake


Lewis Symbols

Lewis Symbols for Selected Elements in Periods 1 to 4


Karen C. Timberlake


Study Check

Write the electron-dot symbol for each of the following

elements: Cl, C, N.


Karen C. Timberlake


Solution

Write the electron-dot symbol for each of the following

elements: Cl, C, N.

C NCl


Karen C. Timberlake


Atomic size

• is determined by the atom’s atomic radius, the distance

between the nucleus and the outermost electrons.

• increases for representative elements from top to bottom

of the periodic table.

• decreases within a period as a result of increased

number of protons in the nucleus.

Atomic Size


Karen C. Timberlake


Atomic Size

For representative elements, the atomic size increases

going down a group but decreases going from left to right

across a period.


Karen C. Timberlake


Ionization Energy

Ionization energy is the energy required to remove one of the

outermost electrons.

Na(g) + energy (ionization) Na+(g) + e−

• As the distance from the nucleus to the valence electrons

increases, the ionization energy decreases.

• The ionization energy is low for metals and high for the

nonmetals.


Karen C. Timberlake


Ionization Energy

Ionization energy decreases

down a group and increases

going across a period from left

to right.


Karen C. Timberlake


Metallic Character

An element with metallic character is one that loses valence

electrons easily.

Metallic character

• is more prevalent in metals on the left side of the

periodic table.

• is less for nonmetals on the right side of the periodic table

that do not lose electrons easily.

• decreases going down a group, as electrons are farther

away from the nucleus.


Karen C. Timberlake


Metallic Character

The metallic character

of the representative

elements increases

going down a group

and decreases going

from left to right

across a period.


Karen C. Timberlake


Summary of Trends in the Periodic Table


Karen C. Timberlake


Study Check

Given the elements C, N, and Cl,

A. which is the largest atom?

B. which has the highest ionization energy?

C. which belongs to Group 5A (15)?

chapter 4 elements and symbols - pbworkschemistry121.pbworks.com/w/file/fetch/101481166/ch4...

Documents