Atomic Structure

What is an Ammonia Molecule?

Nitrogen and hydrogen are both non-metals.
A nitrogen atom has 5 electrons in its outer shell.
Nitrogen is in group 5 of the periodic table.
A hydrogen atom has 1 electron in its outer shell.
Hydrogen can only form 1 bond.

Three hydrogen atoms each share their 1 electron with
nitrogen to form three covalent bonds
and make an ammonia molecule  (NH3).

This is a picture of an ammonia molecule.

The Structure of an Ammonia Molecule

By sharing the two electrons where the shells touch
each hydrogen atom can count 2 electrons in its outer shell
and the nitrogen atom can count 8 electrons in its outer shell.
These full outer shells with their shared electrons
are now stable, and the NH3
molecule will
not react further with other hydrogen or nitrogen atoms.

The molecule can also be shown
without the circles for the shells.

Ammonia Molecule

Note the 3 pairs (6 electrons) shared between the atoms.
Each electron pair is one bond.
This is called a single covalent bond.
Ammonia has three single covalent bonds.

The structural formula of an ammonia molecule is written
Ammonia

There are no ions present (no + or - charges)
in ammonia gas because the electrons are shared,
not transferred from one atom to another.
Ammonia does make some hydroxide ions
when it is dissolved in water to form a weak alkali.


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