The mass number of an atom is calculated by adding the number of protons and neutrons in the nucleus of the atom.
Here's a breakdown:
- Mass Number (A): Represents the total number of nucleons (protons and neutrons) in an atom's nucleus.
- Protons: Positively charged particles found in the nucleus. The number of protons determines the element.
- Neutrons: Neutrally charged particles found in the nucleus.
Formula:
Mass Number (A) = Number of Protons + Number of Neutrons
Example:
Let's say an atom has 6 protons and 8 neutrons.
Mass Number (A) = 6 + 8 = 14
Therefore, the mass number of this atom is 14.
Key Takeaways:
- The mass number is always a whole number.
- The mass number helps differentiate between isotopes of the same element (isotopes have the same number of protons but different numbers of neutrons).
- The mass number is different from the atomic mass, which is a weighted average of the masses of all the isotopes of an element.
