To determine which of the given substances are molecules, we need to understand what constitutes a molecule. A molecule is defined as a group of two or more atoms bonded together.
Now, let's assess each substance provided:
1. [tex]\( H_2O \)[/tex] (water):
- This is composed of two hydrogen atoms and one oxygen atom bonded together.
- Hence, [tex]\( H_2O \)[/tex] is a molecule.
2. [tex]\( O_2 \)[/tex] (oxygen gas):
- This is composed of two oxygen atoms bonded together.
- Therefore, [tex]\( O_2 \)[/tex] is a molecule.
3. NaCl (sodium chloride):
- This is composed of sodium and chlorine ions bonded together in an ionic lattice.
- Ionic compounds like NaCl are not considered molecules.
- Hence, NaCl is not a molecule.
4. [tex]\( CO_2 \)[/tex] (carbon dioxide):
- This is made up of one carbon atom and two oxygen atoms bonded in a linear structure.
- Thus, [tex]\( CO_2 \)[/tex] is a molecule.
5. [tex]\( MgCl_2 \)[/tex] (magnesium chloride):
- This consists of magnesium and chloride ions bonded together ionically in a lattice structure.
- Similar to NaCl, [tex]\( MgCl_2 \)[/tex] is also an ionic compound and not a molecule.
- Therefore, [tex]\( MgCl_2 \)[/tex] is not a molecule.
So, among the given substances, the ones that are molecules are:
- [tex]\( H_2O \)[/tex]
- [tex]\( O_2 \)[/tex]
- [tex]\( CO_2 \)[/tex]
In summary, the molecules are:
[tex]$ H_2O, O_2, \text{ and } CO_2. $[/tex]
