cussed. For the formation of a covalent bond, the involved atoms share at least one pair of electrons with each other. For the formation of an ionic bond, at least one electron is transferred between the atoms of the elements involved. Charged particles or ions are formed that are linked with each other through the force of opposite electrical charges operating between them. The two distinct types of chemical bonding occur in pure forms but often also in a range of intermediate mixed types. Differences in the electronegativity of atoms linked together by covalent bonds causes the formation of polar covalent bonding, where the binding electrons are shared unequally by the two partner atoms involved. Polar covalent bonding is responsible for establishing physical interaction forces holding different molecules together without resulting in chemical changes. One special type is the hydrogen bridge that forms between a hydrogen atom and two neighbouring electronegative elements, e.g. oxygen.

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