Putting Atoms Together

Learning Goals I will be able to identify the difference between ionic and covalent compounds.

I will be able to count the number of atoms in compounds and molecules.

Key Terms Molecule – two or more atoms joined together by a chemical bond �

Chemical formula – tells us the type and number of atoms in a moleculeeg. CaCl2

Subscript – tells us the number of each atom in a chemical formula

Diatomics – a molecule that is made up of two atoms of the same element. H2 O2 F2 Br2 I2 N2 Cl2

Why do elements form compounds? Most elements on their own are not stable. �

To be stable, an element needs 8 electrons in their valence (outer) shell this is called the octet rule �

So…elements form compounds to get 8 electrons.

Ionic Compounds Formed by a metal and a nonmetal � They have ions (charged particles) � Metals: positively charged (cation); give up/lose electrons � Nonmetals: negatively charged (anions); take/gain electrons �

Molecular/Covalent Compounds Formed by two or more nonmetals � �

They share the electrons �

Counting Atoms Identify as ionic or molecular.

How many of each type of element are present in each compound?

C2H6

CaBr2

Al2O3

NH4(BrO3)2

Learning Goals Revisited I will be able to identify the difference between ionic and covalent compounds.

I will be able to count the number of atoms in molecules.

Please Complete … Counting Atom Worksheet

p261 #2, 3, 5, 6a, 7, 8