Consider the following atoms in which X represents the chemical symbol of the element: (4.4, 4.5) ¹⁶₈X ¹⁶₉X ¹⁸₁₀X ¹⁷₈X ¹⁸₈X c. Which atoms have the same mass number?

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. This results in different mass numbers for the isotopes. For example, in the question, the isotopes of element X are represented with varying mass numbers, indicating they are isotopes of the same element.

The mass number of an atom is the total number of protons and neutrons in its nucleus. It is represented as the upper left number in the isotope notation (e.g., ¹⁶ in ¹⁶₈X). Understanding mass numbers is crucial for identifying isotopes and determining which atoms have the same mass number.

The atomic number is the number of protons in the nucleus of an atom and determines the element's identity. It is represented as the lower left number in the isotope notation (e.g., ₈ in ¹⁶₈X). While isotopes of an element share the same atomic number, they differ in mass number due to variations in neutron count.