Chapter 2

Atomic Structure

Law of Conservation of Mass

• Mass can be

• The total mass of the

Law of Constant Composition

• Water is water, no matter where you get it; H2O is H2O

• The elements in a compound are present in a

Percent Composition

• Percent by mass of an element in a compound.–

Practice

• Determine the percent composition of calcium phosphate, Ca3(PO4)2.

Dalton’s Theory• All matter is composed of• The atoms of any one element are • .• Atoms of different elements have

different masses.• Compounds are

• In reactions, atoms are exchanged to form new compounds.

Atomic masses

• Relative.

• Based on carbon-12.

• Isotopes.

• Mass numbers on Table reflect abundance of isotopes.

Atomic Number

• Tells you… 1

H

Structure

• Protons–

• Neutron–

• Electron–

Mass Number

• Tells you–

– H1.00794

Calcium

• Atomic number = –

• What is the charge?

Ions

• Gain or lose –

• Octet Rule:–

Calcium Ion

• Has ‘lost’ 2 electrons

• What is the charge?

Sulfide Ion

• Has gained two electrons

• What is the charge?

Isotopes• Identified by mass number

• C-12, C-13

• Alternate notation– – C

12

6

Determining Average Mass

• Ave = (mass of isotope 1 x % abundance as a decimal) + (mass of isotope 2 x % abundance as a decimal)

• H-1 = 99%

• H-2 = 0.88%

• H-3 = 0.12%

Average Atomic Mass

• What is the average mass of element Q? The abundances are:– Q-54 42%– Q-52 20%– Q-57 10%– Q-58 28%

Periodic Table

• Label appropriately…

• Properties of elements

• Tables 2.2 and 2.3

• Explained by organization in atom

Electromagnetic Radiation

• Electromagnetic spectrum

• Radio waves cosmic rays

• Visible light is small portion

Electromagnetic Radiation

• Speed of light in air Electromagnetic radiation moves through a vacuum at speed of

• Since light moves at constant speed there is a relationship between wavelength and frequency:

Wavelength and frequency are inversely proportional

Practice

• What is the wavelength of light that has a frequency of 2.51 x 1016s-1?

Electromagnetic Spectrum

Emission Spectra

• See figure 2.10, p 51

• Radiation emitted by an ‘excited’ atom

• Color is specific to the atom

• Fireworks

LineLineSpectrumSpectrum

• Elements in gaseous states give off colored

light– High

temperature or high voltage

– Always the same

– Each element is unique

• Spectra

Line SpectrumLine Spectrum• Ground state

–

• Excited state–

– Farther from nucleus–

Line SpectrumLine Spectrum• Electron falls from higher energy

level to lower

• Color of light emitted depends on difference

Line SpectrumLine Spectrum• Each band of color is produced by

light of a different • Each particular wavelength has a

definite

• Each line must therefore be produced by emission of

Absorption Spectra

• Radiation

• Used as a tool to measure concentration

Model of the Atom

• Niels Bohr

• Solar system model

• Explains Hydrogen

The Bohr AtomThe Bohr Atom•Model didn’t seem to work with atoms with more than one electron

•Did not explain chemical behavior of the atoms

Beginnings…Beginnings…

• Max Planck (1858-1947)– Proposed that there is a fundamental

restriction on the amounts of energy that an object emits or absorbs,

• Energy is released in

BeginningsBeginnings

• A quantum is a finite quantity of energy that can be gained or lost by an atom

E =

v =

h = 6.626 x 10-34 J/s

• This constant, h, is the same for all electromagnetic radiation

Practice

• Determine the energy of light with a frequency of 2.22 x 1019 Hz

Quantum numbers

• There are 4

• Tell you how

Principal Quantum Number

• The first quantum number

•

• Corresponds to the

• Value of

• Symbolized by n

Azimuthal Quantum Number

• The second quantum number

• Tells you the

• Symbolized by l

• Has values of 0 to n-1

• Usually shown as

OrbitalsOrbitalsEach sublevel (orbital) has a specific shape

http://daugerresearch.com/orbitals/

Quantum NumbersQuantum Numbers

• Orbital Quantum Number:– Indicates the shape of an orbital– (subshell or sublevels)– s, p, d, f Principal Quantum # Orbital Quantum #

1 1s2 2s, 2p3 3s, 3p, 3d4 4s, 4p,

4d, 4f

Magnetic Quantum Number

• The third number

• Tells you the

•

• Has values of +l to -l

Orbitron

• For a full view of the different orbital shapes, visit

• http://www.shef.ac.uk/chemistry/orbitron/index.html

Spin Quantum Number

• Final quantum number

•

• Electrons behave like little magnets (spin gives magnetism)

• Value of + or – ½ or…

Putting it all together

• Table 2.6 and 2.7

• Orbital arrangement on the periodic table

• Electron configuration

• Aufbau principal– “Building up’

Pauli Exclusion Principal

• No more than

• No electron can have the

Hund’s Rule

• Electrons will fill

• Applies to p, d, and f orbitals

• Electrons (little magnets) repel each other if they have the same spin

Rules for Orbital FillingRules for Orbital Filling

• Pauli’s Exclusion Rule–

• Hund’s Rule–

1s 2s 2p 3s 3p

Rules for Orbital FillingRules for Orbital Filling• Aufbau

– The order of fillingis from the

bottom (low energy) up

– Due to energy levels

Rules for Orbital FillingRules for Orbital FillingDiagonal Rule

The order of filling once the d &

f sublevels are being filled

Due to energy levels

Quantum NumbersQuantum Numbers

• Spin Quantum Number:– Indicates two possible states of an electron in

an orbital

Type of Orbital Number of Orbitals

s 1 ( )

p 3 (x, y, z) ( , , ,)

d 5 ( , , , , )

f 7

Each orbital holds a maximum of 2 electrons

Application of Quantum Application of Quantum NumbersNumbers

• Several ways of writing the address or location of an electron

• Lowest energy levels are filled first• Electron Configuration: using the diagonal

rule, the principal quantum number (n), and the sublevel write out the location of all electrons

12C: 32S:

1s22s22p63s23p4

1s22s22p2

Application of Quantum Application of Quantum NumbersNumbers

• Orbital filling electron diagram: using Hund’s rule and the diagonal rule write out the location of all electrons

• See examples on whiteboard

Chapter 1

• States of matter

• Classification of substances– Mixtures– Pure substances, etc

• Methods of separation of mixtures

Chapter 1

• Measurement

• Units

• Conversions

• Significant figures, calculations

Chapter 1

• Density and calculations

• Temperature and conversions

• Specific heat and calculations

Chapter 2

• Dalton’s ideas

• Percent composition

• Interpretation of the table– Masses, atomic number, etc

• Isotopes and average weighted mass

Chapter 2

• Quantum numbers

• Orbitals

• How to put them together…