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1. Nov 22, 2014

wcui2525

I have a school quiz very soon, and I am having much troubles with the reviews. Can you help please.

In the NH4 bond, how many valance electrons does the N use?

2. Nov 22, 2014

Staff: Mentor

No such thing as NH4 (charge is important), and also there is no such thing as "NH4 bond" - in the NH4+ there are four bonds between atoms.

Try to draw the Lewis structure.

3. Nov 22, 2014

wcui2525

I emailed my teacher, and she said that she rephrased the question from an ACE practice test. The original question was "How many valence electrons does the nitrogen atom use to form the bonds between nitrogen and hydrogen in an ammonia molecule?"

4. Nov 22, 2014

Drakkith

Staff Emeritus
Well, do you understand the concept of valence electrons and bonding now, or do you still need help? (I'm taking chemistry at the moment too. ;))

5. Nov 22, 2014

wcui2525

I still need help with this problem.

I know ammonia is
H
|
H - N - H
|
H

Where the - and | represent single bonds, but don't get the valance electrons stuff

6. Nov 22, 2014

Staff: Mentor

No, that is not ammonia. Please check the formula.

7. Nov 22, 2014

wcui2525

Oh, here it is:
So why the answer is 3? (valance)

8. Nov 22, 2014

Drakkith

Staff Emeritus
Well, how many valence electrons does the Nitrogen atom have prior to bonding? How about the Hydrogens?

9. Nov 22, 2014

wcui2525

Nitrogen has 5 valance before bonding. Hydrogens have 1 each.

10. Nov 22, 2014

Drakkith

Staff Emeritus
Okay. And when each hydrogen bonds to the nitrogen, what happens in that bond? What is each atom doing with its own electrons?

11. Nov 22, 2014

wcui2525

Oh, I get it now. So Nitrogen is sharing 3 electrons, 1 with each hydrogen.

12. Nov 22, 2014

Drakkith

Staff Emeritus
Exactly! Each bond represents a pair of electrons, with one electron given up for sharing by each atom. This leaves 2 of the original 5 valance electrons of Nitrogen left over. They end up being a lone pair, as shown by the two dots at the top of the N in your diagram.

13. Nov 23, 2014

DrDu

Note that it is "valence", which has nothing to do with the moovie " The man who shot Liberty Valance".