Concept:Nitrogen can share its valence electrons to form a maximum of
4 covalent bonds by using its unpaired electrons and its lone pair.
Explanation:Nitrogen has the electronic configuration
1s22s22p3.
It has three unpaired electrons in the
2p orbitals.
These three unpaired electrons form three normal covalent bonds.
Nitrogen also has one lone pair of electrons in the
2s orbital.
This lone pair can be donated to an acceptor atom or ion to form one coordinate covalent bond.
Coordinate covalent bonds are counted as covalent bonds.
In ammonium ion,
NH4+, nitrogen forms
3 normal covalent bonds and
1 coordinate covalent bond.
Therefore, the total number of covalent bonds formed by nitrogen is
3+1=4.
Nitrogen cannot form more than
4 bonds because it has no d-orbitals to expand its octet.
Answer:D.
4