7th grade chemistry final test sem. 2

Please answer the following questions briefly.
1. what is atom?
2. What is meant by nucleon, proton and neutron?
3. what is isotope?
4. Please define Noble gas!
5. why do atoms form ions?
6. what is the difference of ionic bonding and covalent bonding?
7. please give an example for ionic bonding and covalent bonding