I can help you! What is your question?
Answer:
1) Constructive Interference
2) Hits a surface and bounces back
3) Antinodes
a core of protons and neutrons surrounds by electrons
If you mean what group of elements react the most, the answer is the alkali metals and the halogens because they both only either need to gain or lose one electron. If you mean the most reactive element, it would be fluorine because it has the most electronegativity.