Q1. What is an element?

Ans. It is a substance that cannot be split into other substances.

Water is not an element because it can be split into the gases oxygen and hydrogen. Oxygen and hydrogen are elements because they cannot be split. Every element has its own atomic number. This is the number of protons in its nucleus, which is balanced by the same number of electrons.

What are electrons shells.

Q7.What are electrons shells?

Electrons behave as if they are stacked around the nucleus at different levels, like the layers of an onion. These levels are called shells, and there is room for only a particular number of electrons in each shell. The number of electrons in the outer shell determines how the atom will react with other atoms. An atom with a full outer shell, like the gas argon, is unresponsive. An atom with room for one or more extra electrons in its outer shell, like oxygen, is very reactive.


Q9. What is the nucleus?

Ans. Most of an atom is empty space, but right at its center is a very tiny area that is densely packed with particles much bigger than electrons. This is the nucleus, and it usually contains two kinds of nuclear particle-neutrons with no electrical charge, and protons with a positive electrical charge (opposite to the negative charge of electrons).