How many total valence electrons are available in the ion #NO_3-#?
The most important thing to keep in mind here is the fact that you're dealing with an anion, which automatically tells you that you have excess electrons.
In this case, the
In your case, the nitrate anion contains
- one nitrogen atom
- three oxygen atoms
Oxygen, which is located in period 2, group 16, will have a total of six valence electrons.
This means that the nitrate anion will have a total number of valence electrons equal to - do not forget about the extra electron that gives the ion its
# overbrace(1 xx 5)^(color(red)("one N atom")) + overbrace(3 xx 6)^(color(blue)("three O atoms")) + overbrace(color(white)(a)1color(white)(a))^(color(purple)("extra electron")) = color(green)("24 e"^(-)#