Electrons in Atoms

How are they arranged?

They are arranged around the nucleus by energy levels.

Aufbau Principle

Fill the lowest energy orbital first.

Hund's Rule

Just like how you wouldn't sit next to a stranger on an empty bus, place electrons in empty orbitals at the same energy before doubling up.

Pauli Exclusion Principle

Electrons sharing an orbital have opposite spins.

Noble Gas Configuration

1. Find the element on the periodic table

2. Go backward to the nearest noble gas (far right column)

3. Put noble gas in brackets

4. Continue writing the rest of the configuration

Valence Electrons

The outermost electrons: the ones that are lost, gained, or shared in chemical reactions.

The number of valence electrons allows us to predict the bonding pattern of elements.

Electron Configurations of Ions

Positive: take away electrons from highest numbered shell.

Negative: fill in any additional electrons.

Excited State

If an atom is in an excited state then an electron can be in a higher energy level.

S diagram

sphere

P diagram

dumbbell

D diagram

clover

a group or family

vertical column in the periodic table

a period

horizontal row in the periodic table

Group 1

alkali metals

Group 2

alkaline earth metals

Groups 3-12

transition metals

F-block

inner transition metals

Group 17

halogens

Group 18

noble gases

Effective Nuclear Charge (Zeff)

the amount of pull actually felt by the valence electrons

Zeff equation

Zeff = Z (number of protons) - S (number of shielding electrons)

ground state

occupying the lowest possible energy levels

excited state

when electrons absorb energy from external source they are promoted to higher energy levels

exceptions

copper and chromium - for both of them 4s^2 turns into 4s^1

metals physical properties

malleable, ductile, high electrical and thermal conductivity

nonmetals

have the opposite physical properties of metals

attraction between nucleus and electrons

the nucleus has a positive (+) charge and electrons have a negative (-) charge so they're attracted to each other

valence shell

outermost electron shell of an atom, determines atom's chemical behavior

shielding electrons

inner electrons, every shielding electron cancels out the charge of one proton

atomic radius

distance from nucleus to valence electrons

ionization energy

That's how hard it is to take a valence electron away from an atom.

If it has high ionization energy, it really doesn't want to lose an electron.

If it has low ionization energy, it lets go easily.

electronegativity

That's how much an atom wants to pull electrons toward itself when it's sharing them in a bond.

A higher electronegativity means it's greedy for electrons.

A lower electronegativity means it's not that interested in pulling electrons.

metalloids physical properties

not malleable or ductile but are luster like metals