12th Class Biology blank Types And Significance Of Chemical Bonds

A chemical bond is an attractive force that links two atoms to form a molecule. Chemical bonds act like a powerful 'glue' that holds atoms close together. Three kinds of chemical bonds are: ionic bonds, covalent bonds and hydrogen bonds.

(1) Ionic Bonds

(i) When an atom loses or gains a valence electron, ions are formed.

(ii) Positively and negatively charged ions are attracted to    one another.

(iii) When this force of attraction holds ions having opposite charges together, it is called ionic bond.

(2) Covalent Bonds

(i) When a covalent bond forms, neither of the combining atoms loses or gains electrons.

(ii) Instead, the atoms form a molecule by sharing one, two or three pairs of their valence electrons.

(iii) The greater the number of electron pairs shared between two atoms, the stronger the covalent bond.

(iv) Covalent bonds are the most common chemical bonds in living organisms.

(v) The compounds that result from them form most of the body's structures.

(3) Hydrogen Bonds

(i) A hydrogen bond is a weak bond it has greater  advantage in biological systems.

(ii) An atom of hydrogen that forms a polar covalent bond with an oxygen atom or nitrogen atom may form hydrogen bond with an electronegative atom.

(iii) The polar covalent bond causes the hydrogen atom to have a partial positive charge\[({{\delta }^{+}})\] of neighbouring electronegative atoms, often oxygen or nitrogen.