What type of bond forms when two atoms share electrons?

• A. Ionic bond
• B. Covalent bond
• C. Hydrogen bond
• D. Disulfide bond

Answer: (B)

A covalent bond forms when two atoms share electrons. This type of bond occurs because both atoms strive to achieve a stable electron configuration, often by completing their outer electron shell. By sharing electrons, each atom can effectively "count" the shared electrons as part of its own valence shell, which leads to increased stability.

In covalent bonding, the shared electrons can be equally or unequally shared, leading to nonpolar or polar covalent bonds, respectively. Nonpolar covalent bonds occur when electrons are shared equally due to similar electronegativities, while in polar covalent bonds, one atom attracts the shared electrons more strongly than the other, resulting in partial positive and negative charges on the atoms.

Understanding covalent bonds is fundamental in chemistry since they are prevalent in organic molecules, including biological macromolecules like proteins, carbohydrates, and nucleic acids.