Chemistry
Define the term 'valency'. With reference to water & ammonia as compounds respectively state the valency of oxygen & nitrogen. Magnesium [2, 8, 2] has valency 2+. Give reasons.
Answer
Valency is the number of hydrogen atoms which can combine with [or displace] one atom of the element [or radical] forming a compound.
In case of water, two atoms of hydrogen combine with one atom of oxygen. Hence, valency of oxygen is 2.
In case of ammonia, three atoms of hydrogen combine with one atom of nitrogen. Hence, valency of nitrogen is 3.
Valency is also defined as the number of electrons an atom can donate or accept so as to achieve stable electronic configuration of the nearest noble gas. In case of magnesium [2, 8, 2], it donates two electrons to achieve a stable electronic configuration of the nearest noble gas [Neon (2,8)], hence its valency is 2+
Related Questions
Explain the term 'symbol'. State a reason why the symbol of calcium is 'Ca' & of copper is 'Cu'.
Explain the term 'variable valency'. Copper having electronic configuration 2, 8, 18, 1 exhibits variable valency. Give a reason for the same & name the compound CuCl & CuCl2.
State the valencies of the following metallic elements -
(a) Potassium
(b) Sodium
(c) Calcium
(d) Magnesium
(e) Zinc
(f) Aluminium
(g) Chromium
[write each symbol with the valency]
Certain metals exhibit variable valencies which include valencies: 1+, 2+, 3+, & 4+. State the variable valency of the following metals -
(a) Copper
(b) Silver
(c) Mercury
(d) Iron
(e) Tin
(f) Lead
[write each symbol with the variable valency]