To determine which compound contains only nonpolar covalent bonds, let's analyze each one of the given options.
1. [tex]\( O_2 \)[/tex] (Oxygen molecule):
- This molecule is composed of two oxygen atoms.
- Since both atoms are the same, they have the same electronegativity.
- The electrons in the bond are shared equally.
- Therefore, the bond between the two oxygen atoms is a nonpolar covalent bond.
2. [tex]\( HCl \)[/tex] (Hydrogen chloride):
- This molecule consists of one hydrogen atom and one chlorine atom.
- Chlorine has a higher electronegativity than hydrogen.
- This difference in electronegativity causes the electrons to be more attracted to the chlorine atom, resulting in a polar covalent bond.
3. [tex]\( H_2O \)[/tex] (Water):
- This molecule consists of two hydrogen atoms and one oxygen atom.
- Oxygen has a higher electronegativity than hydrogen.
- The difference in electronegativity creates polar covalent bonds between oxygen and hydrogen atoms.
4. [tex]\( NO_3 \)[/tex] (Nitrate ion):
- This molecule is composed of one nitrogen atom and three oxygen atoms.
- The difference in electronegativity between nitrogen and oxygen also leads to polar covalent bonds.
After analyzing these compounds, we can see that:
- [tex]\( O_2 \)[/tex] contains only nonpolar covalent bonds.
- [tex]\( HCl \)[/tex], [tex]\( H_2O \)[/tex], and [tex]\( NO_3 \)[/tex] all contain polar covalent bonds.
Therefore, the compound that contains only nonpolar covalent bonds is:
[tex]\( O_2 \)[/tex]
Thus, the answer is the index number corresponding to [tex]\( O_2 \)[/tex], which is 1.
