Understanding the difference between atomic number and mass number can be a little confusing at first. But don't worry! Once you get it, it will be much easier to understand.

1. Atomic Number (Z):

• The atomic number is the count of protons in an atom's nucleus.
• Each element has its own unique atomic number.
• For example, carbon has an atomic number of 6. This means it has 6 protons.
• In a neutral atom (which means it has no charge), the number of protons is the same as the number of electrons.
• So, knowing the atomic number also helps us understand the charge of the element.

2. Mass Number (A):

• The mass number is the total number of protons and neutrons in an atom’s nucleus.
• For example, if an element has 6 protons and 6 neutrons, its mass number would be 12.
• You find this by adding the number of protons (Z) and the number of neutrons (N): A = Z + N = 6 + 6 = 12.
• The mass number can help us tell apart different forms of the same element.
• For instance, carbon-12 and carbon-14 both have the same atomic number (6), but their mass numbers are different because they have different numbers of neutrons.

3. Isotopes:

• Isotopes are versions of an element that have the same atomic number but different mass numbers.
• This happens because they have different numbers of neutrons.
• Knowing about atomic and mass numbers is important, especially in fields like nuclear chemistry and radioactivity.

So, in short:

• Atomic number = protons
• Mass number = protons + neutrons

Keep it simple, and you'll do great!