dr. s. m. condren chapter 8 electron configuration, periodicity, and properties of the elements

Dr. S. M. Condren

Chapter 8

Electron Configuration,

Periodicity, and

Properties of the Elements

Dr. S. M. Condren

Electromagnetic Radiation

Electromagnetic wave• A wave of energy having a frequency

within the electromagnetic spectrum and propagated as a periodic disturbance of the electromagnetic field when an electric charge oscillates or accelerates.

Dr. S. M. Condren

Dr. S. M. Condren


Electromagnetic wave

• wavelength

• frequency

• amplitude

Dr. S. M. Condren

Dr. S. M. Condren

Quantum Mechanics

Quantum theory• the theory of the structure and behavior of

atoms and molecules.

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Black Body Radiation

http://www.cbu.edu/~mcondren/C11599/BBvis.mov

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= c

where=> frequency

=> wavelength

c => speed of light

Dr. S. M. Condren


Ehi - Elo = hc/where E => energy

h => Planck's constant

c => speed of light

=> wavelength

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Photoelectric Effect

• the emission of electrons by substances, especially metals, when light falls on their surfaces.

Dr. S. M. Condren

Dr. S. M. Condren

Photons

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

Dr. S. M. Condren

Dr. S. M. Condren

Line Spectrum

A spectrum produced by a luminous gas or vapor and appearing as distinct lines characteristic of the various elements constituting the gas.

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Emission Spectrum

The spectrum of bright lines, bands, or continuous radiation characteristic of and determined by a specific emitting substance subjected to a specific kind of excitation.

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Ground State

The state of least possible energy in a physical system, as of elementary particles. Also called ground level.

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Excited State

Being at an energy level higher than the ground state.

Dr. S. M. Condren

Dr. S. M. Condren

Absorption Spectrum

• Light shinning on a sample causes electrons to be excited from the ground state to an excited state

• wavelengths of that energy are removed from transmitted spectra

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Knowing diamond is transparent, which curve best represents the absorption spectrum of diamond (see below)?

A, B, C

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The Atomic Spectrum of Hydrogen and the Bohr Model

Bohr Model for the Hydrogen Atom

mnr = nh/2p

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Bohr Model

Netscape

• NCSU Materials Science site– Chapter 2 Atomic Bonding

• I Atoms and Electrons– slide 2

or

• http://odin.cbu.edu/~mcondren/bohr.html

or through the CHEM 115 homepage

Dr. S. M. Condren

Bohr Atom

Dr. S. M. Condren

Bohr Model

E = -B/n2

where n => quantum number

1, 2, 3, 4, 5, 6, 7, etc

Dr. S. M. Condren

Bohr Model

E = (-2.179 X 10-18 J/part.)

(6.022 X 1023 part./mole)

(1 kJ/103 J)/n2

= (-1312 kJ/mol)(1/n2)

Dr. S. M. Condren

Bohr Model

for hydrogen

ground state: n = 1

excited state: n > 1

Dr. S. M. Condren

Dr. S. M. Condren

Line Spectra

Lyman series => ultraviolet

n > 1 ==> n = 1

Balmer series => visible light

n > 2 ==> n = 2

Paschen series => infrared

n > 3 ==> n = 3

Dr. S. M. Condren

Line Spectra

See CHEMWORKS software

Dr. S. M. Condren

According to the energy diagram below for the Bohr model of the hydrogen atom, if an electron jumps from E1 to E2, energy is

absorbed

emitted

not involved

Dr. S. M. Condren

Heisenberg, Werner1901–76, German physicist

1932 Nobel Prize in physics

A founder of QUANTUM MECHANICS, he is famous for his uncertainty principle, which states that it is impossible to determine both the position and momentum of a subatomic particle (such as the electron) with arbitrarily high accuracy.

Dr. S. M. Condren

Heissenberg Uncertainty Principle

“it is impossible to determine both the position and momentum of a subatomic particle (such as the electron) with arbitrarily high accuracy”

The effect of this principle is to convert the laws of physics into statements about relative, instead of absolute, certainties.

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Orbitals

• region of probability of finding an electron around the nucleus

• 4 types => s p d f

• maximum of 2 electrons per orbital

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Pure Atomic Orbitals

shape # of orbitals / energy level

s spherical 1

p dumbbell 3

d complex 5

f very complex 7

Dr. S. M. Condren

Dr. S. M. Condren

Shapes of Orbitals

http://www.colby.edu/chemistry/OChem/DEMOS/Orbitals.html

Dr. S. M. Condren

Dr. S. M. Condren

Electronic Configurations

• The shorthand representation of the occupancy of the energy levels (shells and subshells) of an atom by electrons.

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Electronic Configuration

shells => energy levels

subshells => orbitals

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Electron Filling Order Diagram

1s

2s 2p

3s 3p 3d

4s 4p 4d 4f

5s 5p 5d 5f

6s 6p 6d

7s

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H atom

1 electron

1s1

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He atom

2 electrons

1s2

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Li atom

3 electrons

1s2, 2s1

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Cl atom

17 electrons

1s2, 2s2, 2p6, 3s2, 3p5

Dr. S. M. Condren


As atom

33 electons

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

or

[Ar] 4s2, 3d10, 4p3

Dr. S. M. Condren

Mn: [Ar]4s2 3d?

How many d electrons does Mn have?

4, 5, 6

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negative ions

add electron(s), 1 electron for each negative charge

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S-2 ion

(16 + 2)electrons

1s2, 2s2, 2p6, 3s2, 3p6

Dr. S. M. Condren


positive ions

remove electron(s), 1 electron for each positive charge

Dr. S. M. Condren


Mg+2 ion

(12-2)electrons

1s2, 2s2, 2p6

Dr. S. M. Condren

How many valence electrons are in Cl, [Ne]3s2 3p5?

2, 5, 7

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For Cl to achieve a noble gas configuration, it is more likely that

electrons would be added

electrons would be removed

Dr. S. M. Condren

Magnetism

• Result of the spin of electrons

• diamagnetism - no unpaired electrons

• paramagnetism - one or more unpaired electrons

• ferromagentism - case of paramagnetism where the substance retains its magnetism

Dr. S. M. Condren

paramagnetic ferromagnetic

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Trends in thePeriodic Table

• atomic radius

• ionic radius

• ionization energy

• electron affinity

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Atomic Radius

• decrease left to right across a period– as nuclear charge increases, number of

electrons increase; however, the nucleus acts as a unit charge while the electrons act independently, pulling electrons towards the nucleus, decreasing size

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Atomic Radius

• increase top to bottom down a group– each additional electron “shell” shields the

outer electrons from the nuclear charge

Zeff = Z - Swhere Zeff => effective nuclear charge

Z => nuclear charge, atomic numberS => shielding constant

Dr. S. M. Condren

Atomic Radius

• increases from upper right corner to the lower left corner

Dr. S. M. Condren

Dr. S. M. Condren

Ionic Radius

• same trends as for atomic radius

• positive ions smaller than atom

• negative ions larger than atom

Dr. S. M. Condren

Ionic Radius

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

Dr. S. M. Condren

Dr. S. M. Condren

Ge is a semiconductor. If half of the Ge atoms of a sample of Ge are replaced with Ga atoms, with what element should the other half of the Ga atoms be replaced in order for this new compound to be isoelectronic with Ge?

Sn, As, Se

Dr. S. M. Condren

Ionization Energy

• energy necessary to remove an electron to form a positive ion

• low value for metals, electrons easily removed

• high value for non-metals, electrons difficult to remove

• increases from lower left corner of periodic table to the upper right corner

Dr. S. M. Condren

Ionization Energies

first ionization energy

• energy to remove first electron from an atom

second ionization energy

• energy to remove second electron from a +1 ion

etc.

Dr. S. M. Condren

Dr. S. M. Condren

Electron Affinity

• energy released when an electron is added to an atom

• same trends as ionization energy, increases from lower left corner to the upper right corner

• metals have low “EA”

• nonmetals have high “EA”

dr. s. m. condren chapter 8 electron configuration, periodicity, and properties of the elements

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