All matter is composed of elements. Each element being composed of atoms of a unique type. Atoms in a pure substance are identical to one another but different from the atoms of a different element. N. Atoms- Elements consist of atoms, an atom is the smallest unit of matter that still retains the properties of the original element. Hydrogen is simplest atom.
Atomic weight is an atom's mass relative to a hydrogen atom.
Atomic number is the number of protons in an atom. Usually, the atomic weight of an element is twice that of its atomic number. The atomic weight of N is 14, of O is 16. The electrons of an element, though not contributing much to the mass of the particle, are important to an atom's interaction with other atoms. Sharing of electrons to form a molecule is called a covalent bond.