Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

The number of protons in an atom indicates what characteristic?

1. The mass number

2. The atomic number

3. The number of electrons

4. The element's charge

The correct answer is: The atomic number

The number of protons in an atom is fundamental to its identity and is referred to as the atomic number. This number uniquely defines an element and determines its position on the periodic table. For instance, an element with one proton is hydrogen, while an element with six protons is carbon. The atomic number not only indicates the specific element but also affects its chemical properties and behavior during reactions. Since protons are positively charged, the atomic number directly relates to the charge of the nucleus and helps balance the negative charge of electrons in a neutral atom. Other options do not accurately represent the role of protons. While the mass number is the sum of protons and neutrons, and the number of electrons typically equals the number of protons in a neutral atom, these do not solely define the characteristic of protons. Additionally, the element's charge refers to the balance of protons and electrons, which is influenced by proton count but is not exclusively determined by it. Thus, the atomic number, directly correlated with the number of protons, is the best description of what that number indicates.