Sure, let's analyze the substances given and determine which one can be classified as an element.
1. [tex]\(H_2\)[/tex]
- [tex]\(H_2\)[/tex] (hydrogen gas) consists of two hydrogen atoms bonded together. Since it is made up of only one type of atom, it is classified as a pure element.
2. [tex]\(NO_3\)[/tex]
- [tex]\(NO_3\)[/tex] is the nitrate ion, which contains nitrogen and oxygen atoms. Since it is composed of more than one type of atom, it is classified as a compound, not an element.
3. NaCl
- Sodium chloride (table salt) is composed of sodium (Na) and chlorine (Cl) atoms. This makes it a compound because it involves more than one type of element.
4. [tex]\(H_2SO_4\)[/tex]
- Sulfuric acid ([tex]\(H_2SO_4\)[/tex]) is composed of hydrogen, sulfur, and oxygen atoms. Since it involves multiple types of elements, it is also a compound.
Given this analysis, the pure substance that can be classified as an element is [tex]\(H_2\)[/tex].
Thus, the correct answer is:
[tex]\[ \boxed{1} \][/tex]
[tex]\(H_2\)[/tex] is the only pure substance in the given list that can be classified as an element.
