To find the mass of an atom, you need to consider the contributions of its protons, neutrons, and electrons. Here's a step-by-step process to determine the mass of an atom:
Identify the element: Determine which element's atom you want to calculate the mass for. Each element has a unique number of protons in its nucleus, known as the atomic number (Z).
Find the atomic mass: Look up the atomic mass of the element. The atomic mass is typically listed on the periodic table and represents the average mass of all the isotopes of that element, taking into account their relative abundances. It is usually expressed in atomic mass units (amu) or unified atomic mass units (u).
Determine the number of protons: The atomic number (Z) of the element tells you the number of protons in the nucleus. This value remains constant for a specific element.
Determine the number of neutrons: Subtract the atomic number from the atomic mass to find the number of neutrons. Neutrons are electrically neutral particles found in the nucleus. The number of neutrons can vary among different isotopes of the same element.
Neutrons = Atomic mass - Atomic number (N = A - Z)
Calculate the total mass: Add the number of protons and neutrons to find the total mass of the atom. Both protons and neutrons have a mass of approximately 1 atomic mass unit.
Total mass = Number of protons + Number of neutrons
It's important to note that the mass of electrons is negligible compared to the mass of protons and neutrons, so they are often excluded when calculating the mass of an atom.