Mass Number - Explanation

The mass number of an atom is the total number of protons and neutrons in its nucleus. It is represented by the symbol "A". The mass number is an important characteristic of an atom, as it determines the atom's mass and is used to calculate its atomic mass.

The mass number is not the same as the atomic number, which is the number of protons in the nucleus. Atoms of the same element can have different mass numbers if they have different numbers of neutrons. These atoms are called isotopes.

Study Guide - Mass Number

1. Definition: The mass number (A) of an atom is the total number of protons and neutrons in its nucleus.
2. Calculating Mass Number: To calculate the mass number of an atom, simply add the number of protons and neutrons together.
3. Isotopes: Atoms of the same element with different mass numbers are called isotopes. Isotopes have the same atomic number but different mass numbers due to varying numbers of neutrons.
4. Importance: The mass number is crucial in determining the overall mass of an atom and is used to calculate the atomic mass of an element.
5. Representation: The mass number is usually written as a superscript before the chemical symbol of the element (e.g., ¹²C for carbon-12).
6. Example: For an element with 6 protons and 6 neutrons, the mass number would be 12 (6 protons + 6 neutrons = 12).

Understanding the concept of mass number is essential in comprehending the structure and properties of atoms. It is also fundamental in various fields such as chemistry, physics, and nuclear science.