I believe they are called Energy Levels or Energy Orbitals.
When a electron moves from higher shell to lower shell ,it releases energy because if it goes to lower shell without releasing energy then it will unable to do that so.as lower electron shells have low energy electrons
Explanation:
here's the answer to your question
double arrow just mean that it's a reversible process, and the reaction can go back and forth.
Explanation:
2H2+O2------->2H2O
its yr balanced equation.
hope it helps
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