To determine which of the given options is both a molecule and a compound, let's analyze each option while keeping in mind the definitions:
- Molecule: A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.
- Compound: A substance formed when two or more different elements are chemically bonded together.
Let's go through each option:
1. [tex]$H_2$[/tex] (Hydrogen molecule):
- This is a molecule because it consists of two hydrogen atoms bonded together.
- However, it is not a compound because it consists of only one type of element (hydrogen).
2. [tex]$Na^+$[/tex] (Sodium ion):
- This is not a molecule because it is a single ion, not a group of atoms bonded together.
- It is also not a compound because it doesn’t consist of different elements bonded together.
3. [tex]$O_2$[/tex] (Oxygen molecule):
- This is a molecule because it consists of two oxygen atoms bonded together.
- However, it is not a compound because it consists of only one type of element (oxygen).
4. [tex]$CO_2$[/tex] (Carbon dioxide):
- This is a molecule because it consists of three atoms (one carbon and two oxygen) bonded together.
- It is also a compound because it contains atoms of different elements (carbon and oxygen) chemically bonded together.
Based on the analysis, the only option that qualifies as both a molecule and a compound is [tex]$CO_2$[/tex].
Thus, the correct choice is:
[tex]$4$[/tex]: [tex]$CO_2$[/tex]
