Reading the table, valency and group trends
Answers are for parents and teachers.
1
Write the electron arrangement of magnesium (12 electrons) and give its period and group.
2, 8, 2; period 3, group 2A.
2
Draw the Lewis dot picture of phosphorus (15 electrons) and find its valency.
Phosphorus is 2, 8, 5: five dots, one pair and three single dots, so the valency is 3.
3
An element has the arrangement 2, 8, 8, 2. Give its period and group, and say whether it is probably a metal.
Period 4, group 2A; probably a metal, because it has 2 outer electrons.
4
Explain why lithium, sodium and potassium behave alike.
They are all in group 1A, so each has 1 outer electron.
5
Why must we never test alkali metals with water or handle chlorine, bromine or iodine at home?
They are dangerous. Only trained adults use them in a laboratory.