Which of the following occurs when a covalent bond forms?

a. Electrons in valence shells are transferred from one atom to another.

b. Electrons in valence shells are shared between atoms.

c. Partial charges on polar molecules interact.

Verified step by step guidance

1. Identify the definition of a covalent bond: A covalent bond involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding.
2. Analyze option a: This option describes the transfer of electrons from one atom to another, which is characteristic of ionic bonds, not covalent bonds.
3. Analyze option b: This option states that electrons in valence shells are shared between atoms. This aligns with the definition of covalent bonds, where atoms share electrons to achieve stability.
4. Analyze option c: This option describes interactions involving partial charges on polar molecules, which refers to dipole-dipole interactions, a type of intermolecular force, rather than the formation of covalent bonds.
5. Conclude that the correct answer must involve the sharing of electrons between atoms, as this is the defining feature of covalent bonds.