Homework Prob 3.37

[Julia Meno 1D]

Hi! Can someone explain how they figured out the answer to 3.37? It asks us to identify the element "E" in this Lewis structure, and E is said to be in Period 3.

[Sarah_Stay_1D]

Hi! Can someone explain how they figured out the answer to 3.37? It asks us to identify the element "E" in this Lewis structure, and E is said to be in Period 3.

First you just need to count up the total number of electrons in the structure (32 e-). Since there are 3 Cl atoms and we know Cl has 7 valence electrons, 21 of the electrons must be from Cl. There are now 11 electrons left, and 6 of those must be from the oxygen (because it has 6 valence electrons). Now there are 5 electrons left that must come from E. Since the E has 5 valence electrons it must be in group 15. Also, the problem tells you that E is from Period three, which means E must be Phosphorous (P).

[Nhan Nguyen 2F]

For better understanding,
We know E is an atom that is able to take in more than 4 bonds (as we can see in the structure). Atoms in period 3 or later can accommodate for additional electrons (more than the full 8 electron set!)