1. Notes 5 - Periodic Table Families & Groups

2. Periods Period – a horizontal row There are 7 periods
Shows number of energy levels
Ex. Gold (Au) is in period 6; gold atoms have 6 energy levels

3. Groups Group – A vertical column 18 groups –
left 2 are groups 1 & 2
right 6 are groups 3 thru 8
Group shows valence electrons
Ex. Carbon (C) is in group 4; carbon atoms have 4 valence electrons

4. Periods vs. Groups
Elements in same group  similar chemical properties
Elements in same period  very different properties

5. Periodic Law First element in each period – valence of 1
Protons & electrons increase by 1 each box
Last element in each period – valence of 8
Helium is only exception – it has 2