Molecule — Science definition
A neutral group of atoms held together by covalent bonds.
Where it is taught
- Covalent Bonding — Bonding, Formulas & Molecular Structure, Physical Science: Chemistry, Grade 11
In use
In water, the oxygen atom shares one pair with each hydrogen but keeps two pairs entirely to itself; electrons that aren't shared are called lone pairs, and, as you'll see in the next lesson, they quietly shape the whole molecule.
Covalent Bonding
Questions using molecule
Problem 1
A nitrogen molecule (N₂) contains a triple bond. How many electrons are shared between the two nitrogen atoms?
Answer and explanation
6
A triple bond is 3 shared pairs, and 3 pairs × 2 electrons = 6 electrons.
Problem 2
Why can a covalent molecule be polar even though it is electrically neutral?
Hints
State what the supplied observations or conditions establish, and separate that from any assumption.
Answer and explanation
Partial charge separation can create a net molecular dipole without net charge.
Problem 3
A molecule of N₂ has a triple bond. How many shared (bonding) electrons are between the two atoms?
Answer and explanation
6
A triple bond is 3 shared pairs, and 3 × 2 = 6 electrons.
Problem 4
In the Lewis structure of a water molecule (H₂O), how many lone pairs are on the central oxygen atom?
- 4
- 0
- 1
- 2
Answer and explanation
2
Oxygen has 6 valence electrons; 2 are used in the two O–H bonds, leaving 4 electrons — that is 2 lone pairs.