Chemistry Term 1

Hund’s Rule

orbitals of the same energy are filled up individually first

Aufbau Principle

electrons occupy lowest orbital first

Pauli Exclusion Principle

An orbital can only hold 2 electrons, which must have opposite spin

Electron cloud notation example

Sulfur: 1s2, 2s2, 2p6, 3s2, 3s2, 3p4

Periodicity

Referring trends seen in elements, based on position in periodic table.

Nuclear Charge

Adding protons to a nucleus directly increases attraction of the nucleus to the electrons.

Shielding Effect

The phenomenon where inner-shell electrons reduce the effective nuclear charge felt by outer-shell electrons, decreasing their attraction to the nucleus. Increases when moving down groups, not across periods.

Ionisation Energy

The energy required to remove an electron from an atom in its gaseous state. It increases across a period and decreases down a group.

Atomic Radius

The distance from the nucleus to the outermost electron shell of an atom. It decreases across a period and increases down a group.

Ionic Radius

The measure of an atom's ion in a crystal lattice which reflects the size of the ion. It varies based on the ion's charge and the coordination number.

Electronegativity

Ability of an atom to form a bond. Increases left to right and bottom to top. Doesn’t include noble gases.

Electron Affinity

Ability of an atom to accept an electron. Increases left to right and bottom to top.

Why are ionic’s brittle?

Because the charges are arranged to be opposites, if the atoms are moved so that the like charges overlap, they repel each other.

Why are metals malleable?

Because metal arrangements contain a sea of delocalised electrons, the atoms can slide past each other without the charges repelling each other.

Alloy

A mixture of metals (and sometimes non-metals) that enhances the metals properties, or combines properties of different metals.

Tetrahedral bond arrangement

Example: CH4. 4 bonds, no lone pairs. each outer element is 109.5 degrees apart.

Pyramidal bond arrangement

Example: NH3. 3 bonds, 1 lone pair. each outer element is 107 degrees apart.

Trigonal Planar bond arrangement

Example: BF3. 3 bonds, no lone pairs. each outer element is 120 degrees apart.

Bent bond arrangement

Example: H2O. 2 bonds, no lone pairs. each outer element is 104 degrees apart.

Linear bond arrangement

Example: CO2. 2 bonds, no lone pairs. each outer element is 180 degrees apart.

Ionic Bonding and properties of ions

Metal + non-metal, lattice crystal formation. Very high boiling point and melting point. Brittle. Only conductive when molten or dissolved. Most are soluble.

Metallic Bonding and properties of metals