Question

How are molecules and elements formed \[?\]

Answer 1

Hint: According to Dalton’s atomic theory, all matter is composed of indivisible building blocks called atoms (which was later disapproved). Atoms can be defined as the smallest part of an element that can take part in a chemical reaction. Matter can be classified into mixtures and pure substances.

Complete answer:
Atoms of the same or different kinds combine together through chemical reactions to form molecules. Molecules can be diatomic, triatomic or polyatomic based on the number of atoms in it. Furthermore, they can also be classified as homonuclear and heteronuclear molecules based on the types of components in it. If it is made of a single component, it is called homonuclear and otherwise it is called heteronuclear. For e.g., ${N_2}$ is a homonuclear molecule and $N{H_3}$ is a heteronuclear molecule. The former is diatomic while the latter is polyatomic. ${O_2}$ is a homonuclear diatomic molecule , while $CO$ is a heteronuclear diatomic molecule.${O_2}$
Materials that contain only a single substance are called pure substances. It can be further classified into elements and compounds. An element is the basic substance that is made from a single type of atom or, “all atoms of an element are identical “ (Dalton’s atomic theory) . Two or more atoms of the same element or different elements combine in definite proportions to form a molecule. Based on the physical and chemical properties, elements can be divided into metals, nonmetals and metalloids.

Note:
Lighter elements like hydrogen (H), helium (He) were formed at the time of ‘Big Bang’ when the universe developed. Cooling of gases and residues from it resulted in the formation of stars. Atomic reactions that happened in stars developed the formation of other elements. In the periodic table, we have only $90$ naturally occurring elements. The rest are man-made.