Question

Why do different elements have different values of atomic mass (previously called atomic weight)?

a) Number of protons in the nucleus
b) Number of neutrons in the nucleus
c) Total number of electrons
d) Atomic radius

Answer 1

Different elements have different atomic masses due to variance in the number of neutrons within their nuclei; the atomic number is the count of protons and remains constant for a given element, which means atomic mass varies primarily because of neutrons, including among isotopes.

Step-by-step explanation:

Different elements have different values of atomic mass because of the varying number of neutrons in their nuclei. The atomic mass is the sum of the numbers of protons and neutrons an element contains. Since the number of protons, known as the atomic number, is fixed for an element, it is the number of neutrons that can differ, even among isotopes of the same element. Hence, the difference in atomic mass between elements primarily arises from the difference in the number of neutrons they possess.

Isotopes of an element have the same number of protons but different numbers of neutrons. This means that while they share the same chemical properties, their atomic mass varies. For instance, chlorine has isotopes with atomic masses of 35 and 37 due to the presence of different numbers of neutrons.