2.6 and 2.7 – Molecular and Ionic Compounds

Molecules and Chemical Formulas

• Atoms bind to other atoms to form molecules• Ionic Bonding: Giving and taking electrons (Metal-

nonmetal bond)• Covalent Bonding: Sharing electrons (nonmetal-

nonmetal bond)• There are gasses that are bound to themselves as

elements:Hydrogen = H2 Nitrogen = N2 Oxygen = O2

Fluorine = F2 Chlorine = Cl2 Bromine = Br2

Iodine = I2

You need to memorize these!

The Hockey Stick and Puck

Formulas

• We can represent molecules with molecular and empirical formulas.• Molecular Formula = shows actual number of

atoms in a molecule.

• Empirical Formula = shows ratio of atoms in a molecule.

22OH

HOOCH2

CLASS EXAMPLE

Determine the empirical formula for the following compounds:1. C6H12O6

2. N2O

TRY IT OUT!

1. Determine the empirical formula of the following compound: B2H6

2. Is this a molecular or empirical formula: N4O6?

Ions and Ionic Compounds

• Recall, an ion forms when an atom gains or loses electrons• Elements/compounds will gain or lose electrons in

order to achieve a full outer valence shell.• Cation – A positively charged ion that forms when

electrons are lost• Anion – A negatively charged ion that forms when electrons are gained.

Cl Cl-

Na Na+

Gains 1 electron, so it ends with a

negative 1 charge

IONIC ATTRACTION

• Just like opposite poles of a magnet attract, oppositely charged ions attract.• Here, our positively charged

Sodium Ion and negatively charged Chlorine Ion are attracted.• They remain ions, but stick

together in a lattice (3D grid pattern) as other ions join them.

Cl- Na+

Cl- Na+

Cl-Na+

Na+

Cl-

Determining Ionic Formulas

• To determine the ionic formula that forms between two ions you need to do a few steps before beginning:1. Make sure you have both a metal and non-

metal. This indicates that an ionic bond will form

2. If a polyatomic ion is present, then make sure to put parentheses around it before beginning

Na+ O2-

Na2O

K2+

NO3

-

K(NO3)

2

CLASS EXAMPLE

Determine the formula when the following join in an ionic bond:1. Sodium and oxygen2. Potassium and phosphate

TRY IT OUT!

1. Lithium and fluorine2. Ammonium and sulfate