Understanding atomic number and mass number is really important for Year 11 students. Let’s break it down into simpler parts:

1. What Are They?

   • Atomic Number (Z): This is the number of protons in an atom. It tells us what kind of element it is.
   • Mass Number (A): This is the total number of protons and neutrons found in the center (nucleus) of the atom.

2. How to Calculate Mass Number:

   • You can find the mass number by using this simple formula:
     A = Z + N
     Here, N is the number of neutrons.

3. Why It Matters:

   • Elements that have the same atomic number act similarly in chemical reactions.

4. About Isotopes:

   • Isotopes are different versions of the same element. They have the same atomic number but different mass numbers.

Understanding these ideas is key to learning about atomic structure, chemical reactions, and the periodic table. These topics are all important parts of Year 11 Chemistry.