Question

Which of the following has a covalent bond?

• A. $NaCl$
• B. $H_{2}O$
• C. $O_2$
• D. None of these

Answer 1

Answer: (B), (C)

The correct options are
B $H_{2}O$
C $O_2$

Covalent bond:
$H_{2}O$ : A single water molecule $H_{2}O$ consists of two hydrogen atoms bonded to one oxygen atom. Each hydrogen shares one of its electrons with the oxygen, and the oxygen reciprocally shares one of its electrons with each hydrogen.
$O_2$ is nonpolar because the electrons will be equally shared between the two oxygen atoms. Both oxygens are electronegative, but they are electron-loving in the same measure.
Ionic bond:
$NaCl:$ Na tends to lose its one electron, forming $Na^+$.Cl tends to take on an electron and become $C{l}^{-}$. When sodium and chlorine are combined, sodium will donate its one electron to empty its shell, and chlorine will accept that electron to fill its shell and form ionic bond.