Mendeleev Periodic Law, Modern Periodic Law and s, p, d, f

Mendeleev Periodic Law

Mendeleev explanation that properties of the elements are periodic function of their atomic weights.

Moseley (1913) according to this law physical & chemical properties of the elements are periodic functions of their atomic numbers.

Elements of group 1 (Alkali metals) with ns² outermost electronic configuration.

· These are all reactive metals with low ionisation enthalpies.

· They lose electrons rapidly to form +1 & +2 ions.

· Metallic character and reactivity increases on going down the group.

These elements belong to group no. 13 to 18.

· These with s – block elements are called representative elements.

· Outermost electronic configuration is varies from ns² np¹ to ns² np^6.

· Element of group 18 (ns² np⁶) are known as noble gases or invert gases.

· Elements of group 17 known as halogens and elements of group 16 known as chalcogens.

· Group 16 & 17 elements have high -ve electron in their outermost shell to attain stable inert gas configuration.

· Non-metallic character increase on moving left to right in period and metallic character increases on moving down in the group.

These are elements of group no. 3 to 12 in centres of periodic table. Also known as the transition elements.

· General outer most electronic configuration is (n-1)d^1-10n^0-2

· These are all metals

· Form colours ions and show variable valences & par magnetism

· Mainly used as a catalyst

· Zn , cd , Hg with configuration (n-1)d¹⁰ns² do not show most of the properties of transition elements.

These have 2 – rows of elements at bottom of periodic table. i.e. lanthanides Ce (z = 58) to Lu (z = 71) Actinides Th (z = 90) to Lr (z = 103) .

· Outer electronic configuration =(n-2) f^1-14 (n-1) d^0-1 ns².

· f – block elements also known as inner transition elements.