Definition
The total count of protons and neutrons within an atom's nucleus.
質量數
The mass number of carbon-12 is 12, indicating it has 6 protons and 6 neutrons.
碳-12的質量數是12，表示它有6個質子和6個中子。
To calculate an atom's mass number, you must add up the number of protons and neutrons in its nucleus.
要計算原子的質量數，你必須將原子核中的質子和中子數量相加。
Isotopes have different mass numbers due to variations in their neutron count.
同位素的質量數不同，因為它們的中子數量有所變化。