Unit 1Matter and Bonding

CHEMISTRY

Why do I have to study chemistry?

Atomic Theory

All elements are composed of atoms

Each element contains similar atoms

Atoms of one element are different from ones from

another

Two or more different atoms bond together to form a

compound

Subatomic Particles

Particle Symbol Charge RelativeMass (u)

Electron e- -1 ~0

Proton p+ +1 1

Neutron n 0 1

Location of Subatomic Particles

10-15 m

electrons

protons

neutrons

10-10 m

nucleus

Characteristics of Electrons

Extremely small mass

Located outside the nucleus

Moving at extremely high speeds in defined

areas around the nucleus called orbitals

Have specific energy levels

In a neutral atom the # of electrons equals

the # of protons

Elements

Are pure substances that cannot be separated into different substances by ordinary processes

Are the building blocks of matter

All atoms of an element have the same number of protons

118 elements known todayExamples: carbon

nitrogengold

Liquid nitrogen.

Name the element found in each!

2.

4. Copper 5. Sulfur 6. Iodine

1. Carbon 2. Sodium 3. Aluminum

Symbols of Elements

Use 1 or 2 letter abbreviations Capitalize the first letter only

Examples:

C carbon Co cobalt

P Phosphorus Ca calcium

Ba Barium Mg magnesium

Symbols from Latin Names

Element Symbol Latin nameCopper Cu cuprum

Gold Au aurum

Lead Pb plumbum

Mercury Hg hydrargyrum

Potassium K kalium

Silver Ag argentum

Sodium Na natrium

Tin Sn stannum

Diatomic elements

• Some elements are composed of two atoms bonded together

• Whenever you write the symbol for these elements a subscript must be written

• Oxygen O2

• Nitrogen N2

• Chlorine Cl2

• Iodine I2

The Periodic Table

Represents physical and chemical behavior

of elements

Arranges elements by increasing atomic

number

Repeats similar properties in columns known

as chemical families or groups

Groups of Elements

Vertical columns on the periodic table

Similar physical properties

Similar chemical properties

Representative Groups

Group 1 Alkali Metals

Group 2 Alkaline Earth Metals

Group 17 Halogens

Group 18 Noble Gases

Periods on the Periodic Table

Horizontal rows from Group 1 to Group 18.

Numbered 1, 2, 3, ….

Metals- General properties

Located on the left hand side Usually solids Lustrous, ductile, malleable Good conductors of heat and electricity Group 1 and 2 metals react with oxygen to form

metal oxides which can react with water to from bases (alkaline)

Transition metals vary in reactivity, typically hard, high melting points, good conductors of electricity, form ions of variable charge

Non-metals: General properties

Located on the right hand sideCan be solid (S, P,C) liquid (Br2 at room

temperature) or gaseous (O2, F2)Dull and brittle solidsPoor conductors, good insulatorsHalogens are extremely reactiveNobel gases extremely unreactive, but

Xe, Kr, Rn will react reluctantly with F

Metalloids

• Do not fit the standard definition of metals or nonmetals

• Include: Boron, Silicon, Antimony, Germanium, Arsenic, Tellurium

• Located on the “staircase” of the periodic table

Metals and Nonmetals

NONMETALS

METALS

METALS

Transition Metals

Atomic Notation

• Atomic number: The number of protons in the nucleus of an element (smaller number)

• Mass number: The average atomic mass of an element (larger number)

Atomic Symbols

Show the mass number and atomic number

Give the symbol of the element

mass number

23 Na sodium-23

atomic number 11

More Atomic Symbols

16 31 65

O P Zn

8 15 30

__p+ __p+ __p+

__n __ n __n__e- __ e- ___ e-

Energy of Electrons

Electrons in atoms are arranged in levels.

An electron absorbs energy to “jump” to a

higher energy level.

When an electron falls to a lower energy level,

energy is released.

Energy levels are like using a stick shift in a car. The faster you travel the higher gear you use.

The Bohr Model

• First model made to illustrate electron structure

• Provides levels where an electron would most likely to be found

A Bohr model of Nitrogen.

Electron Levels (Shells)

Contain electrons that are similar in energy and

distance from nucleus

Low energy electrons are closest to the nucleus

Higher energy electrons are farther away from the

nucleus

The first shell (1) is lowest in energy, 2nd level

next and so on 1<2<3<4

Many shells also have sublevels

Number of Electrons per shell

Use the formula 2n2, where n is equal to the energy level

n =1 2(1)2 = 2

n =2 2(2)2 = 8

n =3 2(3)2 = 18

Periodic Law

All the elements in a group have the same electron configuration in their outermost shells

Example: Group 2

Be 2, 2

Mg 2, 8, 2

Ca 2, 2, 8, 2

Bohr and Lewis Review

Valence Electrons:

•Electrons with the greatest energy

•Electrons that will react to form compounds

Draw the Bohr Diagram for Al

Draw the Lewis Diagram for O

Draw the Lewis Diagram for the compound formed between Al and O. Name it.

Isotopes

Atoms with the same number of protons,

but different numbers of neutrons.

Atoms of the same element (same atomic

number) with different mass numbers

Isotopes of chlorine

35Cl 37Cl17 17

chlorine 35 chlorine 37

Radioisotopes

• An isotope of an element that is capable of spontaneously emitting radiation in the form of particles and/or gamma rays

• Occur naturally or can be produced artificially

• Ex: Tritium 31H

• Half Life: The time it takes for one 1/2 the nuclei in a radioactive sample to decay

• Uses: Nuclear power, cancer treatment carbon -14 dating

Masses of Atoms

A measuring unit designed for atoms gives

their atomic masses in atomic mass units (u)

An atom of 12C was assigned an exact mass of

12.00 u

The relative masses of all other atoms was

determined by comparing each to the mass of 12C

An atom twice as heavy as 12C has a mass of

24.00 u. An atom half as heavy is 6.00 u.

Atomic Mass

Listed on the periodic table

Gives the mass of “average” atom of each

element compared to 12C

Average atom based on all the isotopes and their

abundance %

Atomic mass is not a whole number

Na22.99

Calculating Atomic Mass

Percent(%) abundance of isotopes

Mass of each isotope of that element

Weighted average =

mass isotope1(%) + mass isotope2(%) + …

100 100

Atomic Mass of Magnesium

Isotopes Mass of Isotope Abundance 24Mg = 24.0 u 78.70%

25Mg = 25.0 u 10.13%

26Mg = 26.0 u 11.17%

Atomic mass (average mass) Mg = 24.3 u

Mg24.3

Learning Check!

Gallium is a metallic element found in

small lasers used in compact disc players.

In a sample of gallium, there is 60.2% of

gallium-69 (68.9 u) atoms and 39.8% of

gallium-71 (70.9 u) atoms. What is the

atomic mass of gallium?

Finding An Isotopic Mass

A sample of boron consists of 10B (mass 10.0 u) and 11B (mass 11.0 u). If the average atomic mass of B is 10.8 u, what is the % abundance of each boron isotope?