A group of atoms held together by chemical bonds is

We must first understand what an atom is in order to respond to this question. Atoms are the smallest piece of matter that may combine to form an element. Electrons and a nucleus (protons and neutrons) are its constituent parts. Every solid, liquid, gas, etc. is made up of atoms.

A molecule is created when two or more atoms chemically bond together. A compound is created when atoms from two or more distinct elements combine. Although not every molecule is a compound, every compound is a molecule. One oxygen atom and two hydrogen atoms combine to make the compound water. Additionally, molecules are collections of atoms joined by covalent connections. Compounds that are molecules are referred to as molecular compounds. It displays the exact number of atoms that are present in a molecule.

Let's now examine the process by which atoms are fused.
Covalent or ionic bonds can be used to bind molecules together. Like hydrogen, which only exists as a hydrogen molecule, many non-metal elements exist in the environment as molecules. Homonuclear molecules are made up of two or more atoms of the same element.

When atoms interact due to their shared electrons, molecules are created. Electrons might accomplish it in two different ways. When two atoms share electrons, the sharing creates a bond that binds the two together. These are referred to as covalent bonds.

So, A group of atoms held together by chemical bonds is molecules.

Hence, option A is correct.