To determine which of the following examples contains an ionic bond, let’s review the options carefully and understand the nature of their bonding.
A. \( CH_4 \) (Methane)
- Methane is composed of one carbon (C) atom and four hydrogen (H) atoms.
- Carbon and hydrogen are both nonmetals, and they share electrons to form covalent bonds. Thus, \( CH_4 \) forms covalent bonds, not ionic bonds.
B. \( H_2O \) (Water)
- Water is composed of two hydrogen (H) atoms and one oxygen (O) atom.
- Both elements are nonmetals, and they also share electrons to form covalent bonds. Therefore, \( H_2O \) possesses covalent bonds rather than ionic bonds.
C. \( O_2 \) (Oxygen molecule)
- It consists of two oxygen (O) atoms.
- The bond between the two oxygen atoms is purely covalent as both atoms share electrons equally. Thus, \( O_2 \) forms a covalent bond.
D. \( CaO \) (Calcium Oxide)
- This compound comprises one calcium (Ca) atom and one oxygen (O) atom.
- Calcium is a metal, and oxygen is a nonmetal. Metals tend to lose electrons, and nonmetals tend to gain electrons.
- Calcium will lose two electrons to form a \( Ca^{2+} \) ion, while oxygen will gain those two electrons to form an \( O^{2-} \) ion.
- This transfer of electrons leads to the formation of positively charged and negatively charged ions, which are held together by electrostatic forces in an ionic bond.
Therefore, the compound that contains an ionic bond from the given options is \( CaO \) (Calcium Oxide).
The correct answer is D.
