Question

What is a molecule?
A. A group of two or more atoms that are chemically bonded together or are tightly held together by attractive forces
B. Smallest particle of the matter
C. Mass unit equal to exactly one-twelfth the mass of a carbon-12 atom
D. The combining power (or capacity) of an element

Answer 1

For solving this question, we need to understand the basic properties of a molecule. A molecule is an electrically charged neutral group which consists of two or more atoms that are held together by a chemical bond. We also know that molecules are distinguished from ions due to the lack of electrical charge.

Complete step by step answer:

As we know that, the smallest physical unit of an element or compound, that consists of one or more atoms in an element and two or more different types of atoms in a given compound.
A single molecule can be as small as only two atoms. When the atoms come together they form an ionic or covalent bond. It also forms stable associations that result in change in the properties of either the atom alone. Then, these new molecules exhibit unique emergent properties. Therefore, a molecule exists when two or more atoms join together to form a chemical bond.
So, the definition of a molecule becomes a group of two or more atoms that are chemically bonded together or are tightly held together by attractive forces.

Therefore the option A is correct.

Note:
We need to keep in mind that a combination of atoms is a molecule. And a compound is a molecule made of atoms from different elements. Thus, all compounds are molecules, but not all molecules are compounds. For example, Hydrogen gas is a molecule, but it is not a compound as it is made of one element.