Q.6 Explain the following terms as used in chemistry: donor atom, acceptor atom, electron gas/ sea theory, electronegativity, ionization energy and octet rule.

1. DONOR ATOM: In an coordinate covalent bond the atom which supplies or donates an electron pair for sharing is called donor atom e.g. when an acid is added to water , it dissociates and gives a hydrogen ions. This reacts with H2O to form H3O+. In this case oxygen of water donates a lone pair of electron to H+ to form a coordinate covalent bond. The oxygen atom of H2O has two lone pairs of electron and acts as an electron pair donor.

2. ACCEPTOR ATOM: In a coordinate covalent bond the atom accepts an electron pair from the donor is called acceptor atom e.g. when an acid is added to water, it dissociates and gives hydrogen ion. The oxygen atom of h2o has two lone pairs of electrons. On the other hand, H+ ion has no electron and acts as an electron pair acceptor.

3. ELECTRON GAS OR ELECTRON SEA: Electron sea theory was o by Drade and Loven. According to this theory the valence electrons of a metal atom are not firmly held by the nucleus due to large size and low ionization potential of metal atoms. These electrons form a sea of electrons and can move easily from one atom to the other.

4. ELECTRONEGATIVITY: The power of an atom to attract a shared pair of electron in a covalent bond is called electro negativity e.g. the electro negativity of hydrogen is 2.1.

5. IONZATION ENERGY: Ionization energy means the the least energy required to expel electron from the outer most shell of a gaseous atom to convert it into a positive ion e.g. the ionization energy of sodium is 5.14eV.

6. OCTET RULE: When an atom has eight electrons in its outer most shell it is said to be stable and does not combine with other atoms to reduce its energy. This is called octet rule. All the noble gases except Helium follow the octet rule.