Final answer:
The atomic mass of an unknown element X is calculated as the sum of the number of protons and neutrons. Atomic mass is correctly represented by option (a): Atomic mass = Number of protons + Number of neutrons.
Step-by-step explanation:
Calculating the Atomic Mass of Element X
To calculate the atomic mass of an unknown element X, you need to first understand that atomic mass is the sum of an atom's protons and neutrons. The atomic number of an element, which is equal to the number of protons in the atom, helps distinguish one element from another. However, the number of neutrons can vary, resulting in different isotopes of the same element. The correct numerical setup for calculating atomic mass is option (a): Atomic mass = Number of protons + Number of neutrons
The mass number A can be expressed as the sum of the atomic number Z (number of protons) and the number of neutrons. Therefore, the number of neutrons is A - Z.
The average atomic mass of an element (if isotopes are considered) can be calculated using the natural abundance of isotopes and their mass numbers with the formula: average atomic mass = f1M1 + f2M2 + f3M3... Where f represents the fraction of the isotope and M represents the mass number of that isotope.