Chapter 17, Problem 33A

To determine

Toidentify: The formulas that represent pure elements.

Answer to Problem 33A

  ${\text{H}}_2\text{,He, Na, Au, and U }$

Explanation of Solution

Introduction:

Elements are the substances that cannot be fragmented by chemical processes. The atomic nuclei of all the atoms in a given element possesses same number of protons. That represents atomic number of that particular element.

The given list is ${\text{H}}_{\text{2}}{\text{, H}}_{\text{2}}\text{O, He, Na, NaCl, Au, U }$

Among the given formulas, ${\text{H}}_2\text{,He, Na, Au, and U }$ represents the pure elements. These are chemical formulas of hydrogen, helium, sodium, gold, and uranium respectively. ${\text{H}}_{\text{2}}$ contains two hydrogen atoms and hence it is a diatomic molecule. ${\text{H}}_{\text{2}}\text{O and NaCl }$ are not elements, they are compounds. Because they are composed of two elements. ${\text{H}}_{\text{2}}\text{O}$ consists of two hydrogen atoms and one oxygen atom. It is a chemical formula of water. $\text{ NaCl }$ is a combination of one sodium atom and one chlorine atom. It is a chemical formula of sodium chloride.

Conclusion:

Therefore, in the given list, ${\text{H}}_2\text{,He, Na, Au, and U }$ represents the pure elements.