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 The electrons absorb or emit energy in discrete amounts as they move from one orbit to another... Excited State Being at an energy level higher than the ground state... Atoms and mole

Chapter 3 CHEMICAL THERMODYNAMICS

Chapter 4 CHEMICAL KINETICS

Chapter 5 CHEMICAL EQUILIBRIUM

Chapter 6 SOLUTIONS

Chapter 7 ACIDS AND BASES

Chapter 8 CHEMISTRY OF METALS

Chapter 9 CHEMISTRY OF NONMETALS

Chapter 10 TRANSITION METALS AND COMPLEXES

1 Brady and Holum, 1996, Chemistry: the Study

of Matter and its Changes,

2 th Ed., John Wiley & Sons Inc New York.

2 Umland, Jean B., 1993, General Chemistry,

West publishing company.

3 Zumdahl, Steven S., 1995, Chemical Principal,

2 th Ed DC Health & company Toronto.

Chapter 1 ATOMIC STRUCTURE AND

THE PERIODIC TABLE

 Understand atomic structure of an atom

including its mass number, isotopes and orbitals

 Know how to account for the structure

of the periodic table of the elements based

on the modern theory of atomic structure

 Understand general trends of several

important atomic properties

FUNDAMENTAL PARTICLES

An atom is composed of three types of

subatomic particles: the proton, neutron, and electron

Particle Mass (g) Charge

Proton 1.6727 x 10 -24 +1

Neutron 1.6750 x 10 -24 0

Electron 9.110 x 10 -28 -1

Atomic Structure

Atoms consist of very small, very dense positively charged nuclei surrounded by clouds of electrons at relatively great distances from the nuclei.

Nuclide Symbol

Mass number = number of protons + number of neutrons

= atomic number + neutron number

Isotopes are atoms of the same element with different masses; they are atoms containing the same number of protons but different numbers of neutrons

ISOTOPES

The three isotopes of Hydrogen

Particle Mass (g) Charge

Proton 1.6727 x 10 -24 +1

Neutron 1.6750 x 10 -24 0

1 amu = 1.660 x 10 -24 g

Atomic weight = 0.7899 (23.98504 amu) +

0.1000 (24.98584 amu) +

0.1101 (25.98259 amu)

THE ATOMIC WEIGHT SCALE AND

ATOMIC WEIGHTS

ELECTRONIC STRUCTURES OF ATOMS

 Why do different elements have such different chemical and physical properties?

 Why does chemical bonding occur at all?

with characteristic formulas?

 How can atoms of different elements give off or absorb light only of characteristic colors

Electromagnetic Radiation

Photons

The quantum of electromagnetic energy, generally regarded as a discrete particle having zero mass, no electric charge, and an indefinitely long lifetime

E = hν = hc/λ

h = Planck's constant = 6.626 × 10−34 J.s

Electromagnetic Spectrum

Dispersion of White Light

EMISSION & ABSORPTION SPECTRA

ATOMIC SPECTRA

In 1913, Niels Bohr (1885–1962):

 The electronic energy is quantized: only certain values of electronic energy are possible.

 The electrons absorb or emit energy

in discrete amounts as they move from one orbit to another.

Bohr Model

Bohr Model

Bohr Model for Hydrogen Atom

Excited State

Being at an energy level higher than the ground state.

Electron Transition in a Hydrogen Atom

Lyman series → ultraviolet

Quantum Mechanics

Theory of the structure and behavior of atoms and molecules.

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The Schrödinger Equation

 Has been solved exactly only for

one-electron species such as the hydrogen atom and the ions He+ and Li2+

 Simplifying assumptions are necessary to

solve the equation for more complex atoms

1 Atoms and molecules can exist only in certain energy states In each energy state, the atom or molecule has a definite energy When an atom or molecule changes its energy state, it must emit or absorb just enough energy to bring it to the new energy state (the quantum condition).

Atoms and molecules possess various forms of

energy Let us focus our attention on their electronic

energies.

Basic Ideas of Quantum Mechanics

2 When atoms or molecules emit or absorb radiation (light), they change their energies.

The energy change in the atom or molecule is related to the frequency or wavelength of the light emitted or absorbed by the equations:

ΔE = hν or ΔE = hc/λ

The energy lost (or gained) by an atom as it goes from higher to lower (or lower to higher) energy states is equal to the energy of the photon emitted

3 The allowed energy states of atoms and molecules

can be described by sets of numbers called quantum

Atomic Orbitals

 An atomic orbital is a region of space around the nucleus in which the probability of finding an electron is high.

 Determined by a set of quantum numbers: n, l, m.

 4 types: s, p, d, f.

Atomic Orbitals, s-type

Atomic Orbitals, p-type

Atomic Orbitals, d-type

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Electronic Configurations

• The shorthand representation of the occupancy

of the energy levels (shells and subshells) of

an atom by electrons

Hund's Rules

Electronic Configuration

As atom (33 electons):

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p3

or[Ar] 4s2, 3d10, 4p3

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How many valence electrons are in Cl: [Ne]3s 2 3p 5 ?

2, 5, 7

For Cl to achieve a noble gas configuration,

it is more likely that:

electrons would be added electrons would be removed

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Regions by Electron Type

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Trends in the Periodic Table

• Atomic radius

• Ionic radius

• Ionization energy

• Electron affinity

Atomic Radius

decrease left to right across a period

Zeff = Z - S

where:

Zeff = effective nuclear charge

Z = nuclear charge, atomic number

S = shielding constant

the lower left corner

Atomic Radius

Atomic Radius

Atomic Radius vs Atomic Number

Ionic Radii

• Same trends as for atomic radius

Ionic Radii

Comparison of Atomic and Ionic Radii

 Positive ions smaller than atom

 Negative ions larger than atom

Isoelectronic Series

• series of negative ions, noble gas atom, and positive ions with the same electronic confiuration

• size decreases as “positive charge”

of the nucleus increases

Ionic Radii

first ionization energy

Energy to remove first electron from an atom

second ionization energy

Energy to remove second electron from a +1 ion, etc

Ionization Energy

Ionization Energy vs Atomic Number

• Result of the spin of electrons

• Diamagnetism: no unpaired electrons

electrons

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