Physical Science EOCT Review

Domain 1: Chemistry-Atomic and Nuclear Theory

and the Periodic Table

Domain 1: Chemistry-Atomic Theory

Dalton’s Atomic Theory (experiment based)

3) Atoms of different elements combine in simple whole-number ratios to form chemical compounds

4) In chemical reactions, atoms are combined, separated, or rearranged – but never changed into atoms of another element.

1) All elements are composed of tiny indivisible particles called atoms

2) Atoms of the same element are identical. Atoms of any one element are different from those of any other element.

John Dalton(1766 – 1844)

Sizing up the Atom� Elements are able to be subdivided into

smaller and smaller particles – these are

the atoms, and they still have properties

of that element

�If you could line up 100,000,000

copper atoms in a single file, they

would be approximately 1 cm long

�Despite their small size, individual

atoms are observable with instruments

such as scanning tunneling

microscopes

Subatomic Particles

Nucleus1.67 x 10-240

Neutron

(no)

Nucleus1.67 x 10-24+1

Proton(p+)

Electron cloud

9.11 x 10-28-1

Electron

(e-)

LocationMass (g)ChargeParticle

The Rutherford Atomic Model• Based on his experimental evidence:

–The atom is mostly empty space

–All the positive charge, and almost all the mass is concentrated in a small area in the center. He called this a “nucleus”

–The nucleus is composed of protons and neutrons

–The electrons distributed around the nucleus, and occupy most of the volume

–His model was called a “nuclear model”

Atomic Number

• Atoms are composed of protons,

neutrons, and electrons

– How then are atoms of one element different from another element?

• Elements are different because they

contain different numbers of PROTONS

• The “atomic number” of an element is

the number of protons in the nucleus

• # protons in an atom = # electrons

Atomic Number

Atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element.

7979Gold

1515Phosphorus

66Carbon

Atomic # (Z)# of protonsElement

Mass Number

Mass number is the number of protons and neutrons in the nucleus of an isotope: Mass # = p+ + n0

15- 31

4233-

10Oxygen -

Mass #e-n0p+Nuclide

8 8 1818

Arsenic 75 33 75

Phosphorus 15 3116

SymbolsSymbols

�� Find each of these: Find each of these:

a)a) number of protonsnumber of protons

b)b) number of number of

neutronsneutrons

c)c) number of number of

electronselectrons

d)d) Atomic numberAtomic number

e)e) Mass NumberMass Number

Br80

35

Isotopes

• Dalton was wrong about all elements of the same type being identical

• Atoms of the same element canhave different numbers of neutrons.

• Thus, different mass numbers.

• These are called isotopes.

Isotopes are atoms of the same element having different masses, due to varying numbers of neutrons.

211Hydrogen-3

(tritium)

111

Hydrogen-2

(deuterium)

011

Hydrogen–1

(protium)

NucleusNeutronsElectronsProtonsIsotope

IsotopesElements occur in nature as mixtures of isotopes.

Isotopes are atoms of the same element that differ in the number of

neutrons.

Atomic Mass� How heavy is an atom of oxygen?

� It depends, because there are different

kinds of oxygen atoms.

� We are more concerned with the average

atomic mass.

� This is based on the abundance (percentage) of each variety of that

element in nature.

� We don’t use grams for this mass because

the numbers would be too small.

Measuring Atomic Mass

• Instead of grams, the unit we use is the Atomic Mass Unit (amu)

• It is defined as one-twelfth the mass of a carbon-12 atom.

– Carbon-12 chosen because of its isotope purity.

• Each isotope has its own atomic mass, thus we determine the average from percent abundance.

To calculate the average:

• Multiply the atomic mass of each isotope by it’s abundance (expressed as a decimal), then add the results.

• If not told otherwise, the mass of the isotope is expressed in atomic mass

units (amu)

Atomic Masses

<0.01%6 protons

8 neutrons

14CCarbon-14

1.11%6 protons

7 neutrons

13CCarbon-13

98.89%6 protons

6 neutrons

12CCarbon-12

% in natureComposition of

the nucleus

SymbolIsotope

Atomic mass is the average of all the naturally occurring isotopes of that element.

Carbon = 12.011

The Periodic Table:

A Preview

� A “periodic table” is an arrangement of elements in which the elements are separated into groups based on a set of repeating properties�The periodic table allows you to easily compare the properties of one element to another

The Periodic Table:

A Preview

� Each horizontal row (there are 7 of them) is called a period�Each vertical column is called a group, or family�Elements in a group have similar chemical and physical properties�Identified with a number and either an “A” or “B”�More presented in Chapter 6

Domain 1: Chemistry-Radioactivity and Nuclear

Chemistry

Types of Radioactive Decay

• Alpha Decay (α)

– Alpha particles are just helium nuclei.

– Mass number = 4 (4 amu)

– Charge = 2+

– Low penetration power (Paper & clothing stop

them.)

• Beta Decay (β)

–Beta particles are just electrons.

–Mass number = 0 (1/1837 amu)

–Charge = -1

–Medium penetration power (Metal foil stops them).

• Gamma Decay (γ)

– Gamma radiation is high energy

electromagnetic radiation.

– Mass number = 0

– Charge = 0

– High penetration power (Thick lead shield

stops them.)

Radioactive Decay of a

Hypothetical 31P Sample

• Simulating Radioactive Decay

– You just won $1,000, but…

– …you can only spend half of it in month 1…

– …half of the remainder in month 2, etc.

– After how many months would you be left with less than $1?

– What is the half life for this prize?

Common Half-Lives &

Radiation*

Alpha4.46 X 109 yearsUranium-238

Alpha, gamma7.0 X 108 yearsUranium-235

Beta, gamma24.1 daysThorium-234

Alpha, gamma75,400 yearsThorium-230

Alpha, gamma1,600 yearsRadium-226

Alpha3.8 days Radon-222

Beta, gamma1,25 X 109 years Potassium-40

Beta5,730 yearsCarbon-14

RADIATIONHALF-LIFEISOTOPE

Radiocarbon Dating

• In the upper atmosphere 14C forms at a constant rate:

+→+147N 1

0n 146C

11H

T½ = 5730 Years +→146C 0

-1β147N

• Live organisms maintain 14C/13C at equilibrium.

• Upon death, no more 14C is taken up and ratio changes.

• Measure ratio and determine time since death.

Nuclear Fission

The atom has been split.

Fission

• splitting a nucleus into two or more

smaller nuclei

• 1 g of 235U =

3 tons of coal

U235

92

Fission• Nuclear chain reaction -

self-propagating reaction, a continuous series of nuclear fission reactions.

• critical mass -the minimum amount of a substance than can undergo a fission reaction and can sustain a chain reaction.

Nuclear Fusion

• Fusion produces the energy of the sun.

• Most promising process on earth would be:

• Plasma temperatures over 40,000,000 K to initiate a self-sustaining reaction (we can’t do this yet).

→H31+ He4

2 + n10H2

1

Fusion

• combining of two nuclei to form one nucleus of larger mass

• thermonuclear reaction – requires temp of 40,000,000 K to sustain

• 1 g of fusion fuel = 20 tons of coal

• occurs naturally in stars

HH3

1

2

1+

Applications of Nuclear

Reactions• Dating of ancient artifacts (Carbon-14).

• Smoke detectors (Americium-241).

• Radioactive tracers in medicine (Iodine-131, barium-140, phosphorus-32).

• Cancer treatment (Cobalt-60).

More Applications of Nuclear

Reactions

• Electricity generation (Uranium-235).

• Artificial (lab-made) elements (beyond Z = 92).

• Bombs (Uranium-235).

• Fusion (Combining two small nuclei to form a large nucleus.)

• Interested in learning more?.

Radioactive Waste Disposal

• Low level waste.

–Gloves, protective clothing,

waste solutions.

• Short half lives.

• After 300 years these materials

will no longer be radioactive.

Radioactive Waste Disposal cont.

• High level waste.

–Long half lives.

• Pu, 24,000 years and extremely

toxic.

• Reprocessing is possible but

hazardous.

–Recovered Pu is of weapons

grade.

Domain 1: Chemistry-Periodic Table

Mendeleev’s Periodic Table

• By the mid-1800s, about 70 elements were known to exist

• Dmitri Mendeleev – Russian chemist

• Arranged elements in order of increasing atomic mass

• Thus, the first “Periodic Table”

Mendeleev

• Left blanks for undiscovered elements–When they were discovered, he

had made good predictions

• But, there were problems:

–Co and Ni; Ar and K; Te and I

A better arrangement

• In 1913, Henry Moseley –British physicist, arranged elements according to increasing atomic number

• The arrangement used today

• The symbol, atomic number & mass are basic items included

The Periodic Law says:• When elements are arranged in

order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

• Horizontal rows = periods– There are 7 periods

• Vertical column = group (or family)– Similar physical & chemical prop.

– Identified by number & letter

Electron Configurations in Groups

1) Noble gases are the elements in Group 8A

• Previously called “inert gases” because they rarely take part in a reaction

• Noble gases have an electron configuration that has the outer s and p sublevels completely full

Electron Configurations in Groups

2) Representative Elements are in Groups 1A through 7A

• Display wide range of properties, thus a good “representative”

• Some are metals, or nonmetals, or metalloids; some are solid, others are gases or liquids

• Their outer s and p electron configurations are NOT filled

1A

2A 3A 4A 5A 6A7A

8A• Elements in the 1A-7A groups

are called the representative elements

outer s or p filling

Valence Electrons in

Representative groups• 1A 1 valence electron

• 2A 2 valence electrons

• 3A 3 valence electrons

• 4A 4 valence electrons

• 5A 5 valence electrons

• 6A 6 valence electrons

• 7A 7 valence electrons

• 8A 8 valence electrons

except He with 2 valence electrons

1 2

3 4 5 6 7

8Helium only has 2 valence electrons

Memorize this rhyme.

• “1+, 2+, 3+, skip, 3-, 2-, 1-, zip”

• This tells you the Ionic charge and oxidation numbers for the elements in the 8 REPRESENTATIVE GROUPS, 1A-8A, as you count form left to right.

Ions

• Some compounds are composed of particles called “ions”– An ion is an atom (or group of atoms) that

has a positive or negative charge

– Atoms are neutral because the number of

protons equals electrons

– Positive and negative ions are formed when

electrons are transferred (lost or gained)

between atoms

Ions• Metals tend to LOSE electrons,

from their outer energy level

– Sodium loses one: there are now more protons (11) than electrons (10), and thus a positively charged particle is formed = “cation”

– The charge is written as a number followed by a plus sign: Na1+

– Now named a “sodium ion”

Ions

• Nonmetals tend to GAIN one or more electrons

– Chlorine will gain one electron

– Protons (17) no longer equals the electrons (18), so a charge of -1

– Cl1- is re-named a “chloride ion”

– Negative ions are called “anions”

Areas of the periodic table

• Three classes of elements are: 1) metals, 2) nonmetals, and 3) metalloids

1) Metals: electrical conductors, have luster, ductile, malleable

2) Nonmetals: gererally brittle and nonlustrous, poor conductors of heat and electricity

Metals

Metals

• Luster – shiny.

• Ductile – drawn into wires.

• Malleable – hammered into sheets.

• Conductors of heat and electricity.

Non-metals• Dull

• Brittle

• Nonconductors- insulators

Areas of the periodic table

• Some nonmetals are gases (O, N, Cl); some are brittle solids (S); one is a fuming dark red liquid (Br)

• Notice the heavy, stair-step line?

3) Metalloids: border the line

– Properties are intermediate between

metals and nonmetals

Metalloids or Semimetals

• Properties of both metals and nonmetals

• Semiconductors

#1. Atomic Size - Group trends

• As we increase the atomic number (or go down a group). . .

• each atom has another energy level,

• so the atoms get

bigger.

HLi

Na

K

Rb

#1. Atomic Size - Period Trends

• Going from left to right across a period, the

size gets smaller.

• Electrons are in the same energy level.

• But, there is more nuclear charge.

• Outermost electrons are pulled closer.

Na Mg Al Si P S Cl Ar

Atomic size and Ionic size increase in these directions:

#2. Trends in Electronegativity

• Electronegativity is the tendency for an atom to attract electrons to itself

when it is chemically combined with

another element.

• They share the electron, but how equally do they share it?

• An element with a big electronegativity means it pulls the

electron towards itself strongly!

Electronegativity Group Trend• The further down a group,

the farther the electron is away from the nucleus, plus the more electrons an atom has.

• Thus, more willing to share.

• Low electronegativity.

Electronegativity Period Trend• Metals are at the left of the table.

• They let their electrons go easily

• Thus, low electronegativity

• At the right end are the nonmetals.

• They want more electrons.

• Try to take them away from others

• High electronegativity.

The arrows indicate the trend: Ionization energy and ElectronegativityINCREASE in these directions

Domain 1: Chemistry-Phases of Matter

Kinetic Theory

• Kinetic means motion

• Three main parts of the theory

– All matter is made of tiny particles

– These particles are in constant motion and

the higher the temperature, the faster they

move

– At the same temperature, heavier particles

move slower.

States of Matter

• Solid

• Particles are tightly packed

• Stuck to each other in a pattern

• Vibrate in place

• Can’t flow

• Constant volume

States of Matter

• Liquid

• Particles are tightly packed

• Able to slide past each other

• Can flow

• Constant volume

States of Matter

• Gas

• Particles are spread out

• Flying all over the place

• Can flow

• Volume of whatevercontainer their in

#1. Boyle’s Law - 1662

Pressure x Volume = a constant

Equation: P1V1 = P2V2 (T = constant)

Gas pressure is inversely proportional to the volume, when temperature is held constant.

• The combined gas law contains all the other gas laws!

• If the temperature remains constant...

P1 V

1

T1

x=

P2 V

2

T2

x

Boyle’s Law

#2. Charles’s Law - 1787The volume of a fixed mass of gas is

directly proportional to the Kelvin

temperature, when pressure is held

constant.

This extrapolates to zero volume at a

temperature of zero Kelvin.

V

T

V

TP

1

1

2

2

= =( constant)

• The combined gas law contains

all the other gas laws!

• If the pressure remains

constant...

P1 V

1

T1

x=

P2 V

2

T2

x

Charles’s Law

#3. Gay Lussac’s Law -1802•The pressure and Kelvin temperature of

a gas are directly proportional, provided

that the volume remains constant.

2

2

1

1

T

P

T

P=

•How does a pressure cooker affect the time needed to cook food?

•Sample Problem 14.3, page 423

�The combined gas law contains

all the other gas laws!

�If the volume remains

constant...

P1

V1

T1

x=

P2

V2

T2

x

Gay-Lussac’s Law

#4. The Combined Gas Law

The combined gas law expresses the

relationship between pressure, volume

and temperature of a fixed amount of

gas.

2

22

1

11

T

VP

T

VP=

Sample Problem 14.4, page 424