Putting Atoms Together

Why do atoms combine? To become more stable by gaining, losing or sharing electrons.

Compound types 1. Ionic 2. Molecular/Covalent

1. Ionic Compounds Formed by a metal and a nonmetal They have ions (charged particles) Metals are cations (positively charged) Nonmetals are anions (negatively charged) The metal gives its electron to the nonmetal

Draw Bohr diagrams for Sodium and Chlorine

How and Why Ionic Compounds Occur In ionic compounds atoms give away electrons to get their 8 electrons. – Metals give their electrons to the non-metals – Metals end up with a positive charge – Non-Metals end up with a negative charge Because the ions are charged they stick together in what is called a crystal lattice structure.

Crystal Lattice

Molecular/Covalent Compound Formed by two or more nonmetals They share the electron(s)

Counting Atoms How many of each type of element are present in each compound? C 2 H 6 CaBr 2 NH 4 BrO 3

How & Why Covalent or Molecular Compounds Occur Atoms like to have 8 electrons in their outer ring. In molecular compounds (two non-metals) the atoms share electrons so that each atom ends up with 8 electrons in the outermost ring. The bond that is formed is called a covalent compound.

Some Common Examples H 2 O water CO 2 carbon dioxide