The correct answer is B) is equal to the number of protons in the nucleus of an atom of that element.
Step-by-step explanation:
The atomic number, which is represented by the letter Z, refers to the number positively charged particles known as protons. This characteristic is key in chemistry and related areas because based on these features elements have different properties and are named. For example, an atom of nitrogen element always contains 7 protons, while one of the gold contains 79 protons. Moreover, this property is not related to the number of neutrons because atoms with the same atomic number might differ in the number of neutrons, which leads to isotopes of the same element.