Crossword Puzzle

1. a very small unit of matter that the particles of an atom consist of radical
4. number the number of protons in the nucleus of an atom
6. the part of the nucleus of an atom that has no electrical charge
11. the smallest part of an element or compound that is capable of independent existence
12. an extremely small piece of matter that is part of an atom, for example an electron, proton, or neutron
15. a type of particle in an atom that has the opposite electrical charge to the charge that a normal particle has
16. an ion that has a positive electrical charge
18. an atom with an electrical force created by adding or removing an electron
20. the path that is taken by an electron around the nucleus of an atom

2. particle the nucleus of a helium atom that is produced by some radioactive substances
3. a part of a molecule consisting of a series of atoms connected in a line
5. a simple molecule that can combine with other molecules to form a polymer
7. a unit for measuring the number of molecules in a substance
8. a particle that is the same size as an electron but has a positive electrical charge
9. the part of the nucleus of an atom that has a positive electrical charge
10. a part of an atom that moves around the nucleus and has a negative electrical charge
13. the central part of an atom, consisting of protons and neutrons
14. the valency of an atom
17. an ion with a negative electrical charge
19. the smallest unit of any substance