Four blocks of elements in the periodic table | مصادر الكيمياء

Four blocks of elements in the periodic table



Four blocks of elements in the periodic table.

1 –  s block elements. Elements of groups 1 and 2 each possessing one and two electrons respectively in the  s orbital of their outermost orbits are together known as  s block elements.

Example :                 Na:  1s2 2s2 2p6 3s1                   Mg:  1s2 2s2 2p6 3s2

Characteristics of s block elements.

a -They are metallic in nature and this character increases down each group.

b –  They are highly electropositive in nature.

c –  Most of them impart characteristic colors to the flame.

d – They generally do not exhibit variable valency.

e – The s block elements are present in groups 1 and 2.

2 –  p block elements. Groups 13, 14, 15, 16, 17 and 18 form together p-block elements in which the- outer­most energy levels have complete s orbitals while  p orbitals have 1 to 6 electrons. The s, p and d orbitals of (n-1) orbit are completely filled.

Example :                 Cl:  1s2  2s2p3s2p5                   O:  1s2s2p4

The s and p block elements are known as representative elements.

3 –  d block elements. These are transition elements of groups 3 to 12 in the center of the periodic table. These contain generally electrons (sometimes only one) in the s orbital of the outermost energy level while their penultimate shell contain l to 10 electrons in d orbitals.

Example :                 Fe:  1s2s2p3s3p3d4s2                   Sc:  1s2s2p3s3p3d4s2

Characteristics of d block elements.

a – These are metallic in nature and are called transition elements.

b – They generally form colored ions in solution.

c – They have tendency to show variable valency .

d –  They have tendency to form complex compounds.

4 –  f block elements. Lanthanides (At No. 57 to 71) actinides (At No. 89 to 103) are called f block elements. They generally contain 2 electrons in the s orbital of the outermost energy level, 1 electron in the d orbital of penultimate shell 1 to 14 electrons in the 4f or 5f orbitals.

Example :                 Ce:  [Xe]4f5d6s2                   Pr:  [Xe]4f6s2



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