<u>Answer:</u> The correct option is A) a nitrogen molecule.
<u>Explanation:</u>
Polar covalent molecules are defined as chemical compounds in which the difference in electronegativity between the atoms is not equal to 0. These molecules are formed by heteronuclear molecules.
Heteronuclear molecules are defined as the molecules which are formed by the combination of more than one type of atom having a different nucleus.
Non-polar covalent molecules are defined as chemical compounds in which the difference in electronegativity between the atoms is equal to 0. These molecules are formed by homonuclear molecules.
Homonuclear molecules are defined as the molecules which are formed by the combination of one type of atom having the same nucleus.
From the given options:
- A) A nitrogen molecule
It is a homonuclear molecule formed by the combination of 2 nitrogen atoms
- B) A nitrogen monoxide molecule
It is a heteronuclear molecule formed by the combination of 1 nitrogen and 1 oxygen atoms
- C) A linear nitrogen oxide molecule
with nitrogen in the center
It is a heteronuclear molecule formed by the combination of 2 nitrogen and 1 oxygen atom and has some dipole moment. Thus, is considered a polar molecule
- D) A bent nitrogen dioxide molecule
with nitrogen in the center
It is a heteronuclear molecule formed by the combination of 1 nitrogen and 2 oxygen atoms and has some dipole moment. Thus, is considered a polar molecule
Hence, the correct option is A) a nitrogen molecule.