question makes no sense lol why is it 4 marks
Yeah exactly wth do they even want me to compare theres nothing to compare for valencies
I think the observation implicit in these questions / comments is important... why is this worth 4 marks? Is it just a mistake, or an indication that something is being missed?
Start by considering the term "valency"... it is more than just the charges in
@wizzkids' table, which tells us about ionic forms. I can use them to predict magnesium phosphide will be Mg
3P
2, for example, but what about the compounds of non-metals?
Then, notice that the period requested is not period 2, which is more chemically straight-forward, but period 3... how does this make a difference?
Period 3 non-metals have the ability to expand valence shells and violate the octet rule as the 3d sub-shell is accessible.
Now, think about the valency implications of phosphorous forming both PCl
3 and PCl
5.
What about sulfur forming H
2S, SCl
2, SOCl
2, SO
2, SO
3, SF
2, SF
4, and SF
6?
Or, chlorine forming Cl
2O, Cl
2O
3, Cl
2O
5, and Cl
2O
7?
I can say that nitrogen has a valency of 3, but is that always true of phosphorous? Are there comparisons that I can make between period 3 and their counterpart period 2 elements, or comparisons with each other within period 3?
I think there is scope to say a lot in answer to this question, both about ionic and covalent compounds...