Atomic Structure and the Periodic Table

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Quantum Numbers

Shells: n = 1,2,3...
Subshells: l = 0,1,2...
Orbitals: ml = ...-1,0,1...
Spin: ms = (1/2), - (1/2)

The Aufbau Principle

When building up the electron confuguration of an atom, electrons are placed in orbitals, subshells and shells in order of increasing energy.

The Pauli Exclusion Principle

Within an atom, no two electrons can have the same set of quantum numbers. Therefore, each electron in any atom has its own distinct set of four quantum numbers.

Hund's Rule

When an electon is added to a subshell, it will always occupy an empty orbital if one is available. Electrons will always occupy an orbital singly if possible and pair up only if no empty orbitals are available.

Diamagnetism

Elements with all their subshells completed.

Paramagnetism

Elements with not all of their subshells completed

Energy of an Electon

Energy of electrons is quantized.

En = (-2.178 X 10^-18) / n^2

En = energy of electron
n = principal quantum number of the electron

Energy and Electromagnetic Radiation

When atoms absorb energy in the form of electromagnetic radiation, electrons jump to higher energy levels.

Delta E = hv = (hc) / lambda

Delta E = energy change
h = Planck's constant, 6.63 X 10^-34
v = frequency of the radiation
lambda = wavelength of the radiation
c = the speed of light, 3.00 X 10^8

Dalton's Elements

First to say there were many kinds of atoms, which he called elements.
Atoms are never created or destroyed in an experiment.

Thomson's Experiment

Atoms are composed of positive and negative charges.

Milikan's Experiment

Calculated the charge of an electron.

Rutherford's Experiment

All of the positive charge in an atom was concentrated in the center and that an atom is mostly empty space.

Quantum Theory

Energy changes do not occur smoothly but rather in small specific steps.

Bohr Model

The use of quantum theory to predict that electrons orbit the nucleus at specific fixed radii

The Heisenberg Uncertainty Principle

It is impossible to know both the position and the momentum of an electron at a particular instant.

The de Broglie Hypothesis

Lambda = (h) / mv

Lambda =wavelength associated with a particle
m = mass of particle
v = speed of partiicle
mv = p = momentum of the particle
h = Planck's constant, 6.63 X 10^-34

Move from left to right across periodic table

Atomic Radius decreases
Ionization Energy increases
Electronegativity increases

Moving down a group

Atomic Radius increases
Ionization Energy decreases
Electronegativity decreases

Cations

Postively charged ions that are smaller than atoms.

Anions

Negatively charged ions that are larger than atoms.

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