- The atomic number is defined only by the number of protons.
- The group number identifies the column in the periodic table.
- The atomic mass corresponds to the total number of protons and neutrons within the nucleus.
- The difference between protons and electrons is irrelevant to the mass calculation.
- Final Answer: \(\boxed{c}\)
Explanation
- Analysis of Atomic Structure and Definitions
The atomic mass of an atom is defined by its nuclear composition. To understand what this means, we must examine the fundamental particles within an atom: protons, neutrons, and electrons. Protons and neutrons reside in the dense nucleus at the center of the atom, while electrons orbit the nucleus. The atomic number of an element, denoted by \(Z\), represents the number of protons in the nucleus and uniquely identifies the element. The group number refers to the vertical columns in the periodic table and indicates elements with similar chemical properties. The sum of the number of protons and neutrons in the nucleus is known as the mass number or atomic mass of an isotope. Finally, for a neutral atom, the number of protons equals the number of electrons.
- Evaluating the Given Options
Now let us evaluate the provided options against these scientific definitions:
AAtomic number represents the number of protons only, so it is not the atomic mass.
BThe group number is a location identifier on the periodic table and does not describe the mass of an atom.
CAtomic mass (or mass number) is the total count of protons and neutrons, which contribute to almost all of the atom's mass. This matches our definition.
DThe difference between protons and electrons in a neutral atom is zero, which bears no relation to the mass of the atom.
Therefore, option (c) is the correct definition.
Examples
Understanding atomic mass is crucial in chemistry for calculating molar masses and predicting the outcome of chemical reactions. For instance, if you are a chemical engineer designing a reaction to create a specific material, you must know the masses of the atoms involved to determine the correct stoichiometric ratios. By knowing that the mass of a Carbon-12 atom is derived from 6 protons and 6 neutrons, you can accurately weigh out the reagents needed to achieve a desired yield in the laboratory.