Which of the following compounds does not contain a covalent bond?

The correct choice indicates that CsF (cesium fluoride) does not contain a covalent bond. This distinction arises from the nature of the interactions between the atoms in CsF. Cesium (Cs) is a metal, and fluorine (F) is a nonmetal. When a metal reacts with a nonmetal, the bonding that typically occurs is ionic rather than covalent. In this case, cesium loses an electron to form a cation (Cs⁺), while fluorine gains an electron to form an anion (F⁻). The electrostatic attraction between these oppositely charged ions constitutes ionic bonding.

In contrast, the other compounds listed involve covalent bonding, which occurs when two nonmetals share electrons. Water (H2O) consists of covalent bonds between hydrogen and oxygen; nitrogen gas (N2) features a triple bond where two nitrogen atoms share a total of three pairs of electrons, and methane (CH4) has four covalent bonds formed by carbon sharing electrons with four hydrogen atoms. Thus, the feature distinguishing CsF from the others is its ionic nature, highlighting the absence of covalent bonds in that compound.