Activity 2. Complete the puzzle below. Clues are given to guide you (Horizontal and vertical).

2. a negatively charge subatomic particle

6. a neutral particle of the atom

7. the weighted average of all the isotopes of an element.

Vertical

1. it tells the number of protons in the atom of an element

3. atoms of the same element have the same atomic number but different mass numbers due to the different numbers of neutron in ther nuclei.

4. a positively charged subatomic particle

5. the small dense region in the atom where protons and neutror are found.​