Final answer:
K2O (potassium oxide) is not formed by a covalent bond but by an ionic bond, where potassium donates electrons to oxygen, forming positive and negative ions that attract each other.
Step-by-step explanation:
The student's question is asking which of the listed compounds is not formed by a covalent bond. Covalent bonds involve the sharing of electrons between atoms. For example, the formation of water molecules (H2O) is due to covalent bonding, where hydrogen and oxygen share electrons to fill their outer shells, providing stability to the molecule. Similarly, I2 and CO2 molecules are held together by covalent bonds.
However, K2O (potassium oxide) is formed through an ionic bond, which is the transfer of electrons from one atom to another, creating ions that attract each other due to opposite charges. Potassium (K) donates electrons to oxygen (O), forming K⁺ ions and O²⁻ ions. Therefore, the correct answer to the question is C. K2O.