13. Which are the simplest pure substances that cannot be broken down into any other substances?

Elements

Explanation:

Each kind of atom is an element. Elements are pure substances that cannot be broken down into simpler substances by ordinary chemical means.

convalent bond :

is a chemical bond formed by the sharing of electron between 2 atoms.

it is the direct chemical bond between 2 atoms.

in bond formation atoms are involved here.

electrovalent bond:

is a chemical bond defined as electroststic attraction between 2 atoms.

it is the electrostatic attraction between 2 atoms.

in bond formation, ions are involved here.

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