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A molecule is formed from two or more atoms of a single element. An example is h2o. two hydrogen atoms and one oxygen atom forming a molecule of water! This question is archived.
Single bond is formed when two electrons are shared between two atoms with similar or low electronegativity difference. The two atoms can be of the same type or different types. For example, when the same atoms are joined to form molecules like Cl 2, H 2, or P 4, each atom is bonded to another by a single covalent bond.