EasyChemistryHigh School (9–10)GeneralThe Periodic Table › Periodic TrendsStructure of the Atom › Electronic Configuration and ValencyConceptual
Why do lithium, sodium and potassium all have a valency of 1?
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Why do lithium, sodium and potassium all have a valency of ? Why do fluorine and chlorine also have a valency of , though they are so different?
Need a reminder? The key ideaShow
Valency is the number of electrons an atom loses, gains or shares to fill its outer shell. With to outer electrons it equals that number; with to it is minus that number; a full shell gives . Cross the valencies to write a formula.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Group 1. Each has one outer electron, which it loses to leave a full shell.
Step 2. Group 17. Each has seven outer electrons and gains one to make eight.
Step 3. The difference. The number is the same, but one family gives an electron away and the other takes one in.
Answer: group 1 loses one electron; group 17 gains one. Both moves give a valency of .
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