Drawing the Lewis Structure for NH4+

Viewing Notes:

  • NH4+ is one of the polyatomic ions that you should memorize. It's one of the few positive polyatomic ions you'll work with.
  • Because NH4+ is a positive ion (called a cation) that means it lost one electron. When we write the Lewis structure for NH4+ we need to subtract one valence electron from out total.
  • For the NH4+ Lewis structure we have a total of 8 valence electrons to work with.

Transcript: Hi, this is Dr. B. Let's do the Lewis structure for NH4+, the ammonium ion. So Nitrogen, on the periodic table, is in group 5, so it has 5 valence electrons. Hydrogen, group 1; we've got 4 of these, though; four Hydrogens, so let's multiply that times 4. And if you see a plus sign, that means you've lost a valence electron. So we've lost one, that's minus one. And 5 plus 4 is 9, minus 1, that's going to be 8. So we have eight total valence electrons. Let's put Nitrogen here. We know that Hydrogen always goes on the outside, so there they go; and we've got four of them. So we'll put those four there. Now what we want to do is put some chemical bonds here. We have eight valence electrons so we'll put 2, 4, 6, 8.

And if we check our octets, Hydrogen only needs 2. So the Hydrogens, they're OK, they all have 2 valence electrons. Nitrogen needs eight valence electrons for a full outer shell, or an octet, and Nitrogen has 8. So we're good. That is the structure for NH4+, the ammonium ion. The only thing we have to do though is, we like to put these brackets around it like this and put a plus sign up there.

So if you drew that real nice as a structural formula, that would look like this right here where the brackets are just making sure you remember that is going to be a plus sign because we lost this electron up here. We have to take account for that.

That's the Lewis structure for NH4+. This is Dr. B., and thanks for watching.