collect the perodic classification of elements and distinguish the elements in s, p, d & f‐ blocks explain the structure
Answers
Explanation:
Elements in the long form of periodic table have been divided into four blocks i.e. s ,p ,d and f. This division is based upon the name of the orbitals which receives the last electron.
S block elements
1)Elements in which the last electron enters the s orbital of their respective outermost shells are called s block elements.
2)s sub shell has only 1 orbital which can accommodate only 2 electrons, therefore, there are only two groups of s block elements.
3)Elements of and group 1(hydrogen and alkali metals) and group 2 (alkaline earth metals) and helium comprises s block element.
4)Hydrogen has only one electron and this enters 1s orbital. The rest of the elements i.e. Li, Na, K, Rb, Cs and Fr receive the last electron in 2s, 3s, 4s, 5s,6s and 7s orbitals.
6)There are 14 s-block elements in the periodic table.
General electronic configuration of s-block elements: ns1-2 where n=2-7
Helium belongs to s – block but its positioning with in the p block along with other group 18 elements is justified because it has a completely filled valence shell and thus exhibits properties characteristic of other noble gases.
Because of its unique behaviour, we shall place hydrogen separately at the top of the periodic table it because:
1) It has a single s-electron and hence can be placed along with alkali metal group.
2)It can also gain one electron to acquire a noble gas configuration and hence can be placed along with halogens.
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P block elements
Elements in which the last electrons enter any one of the three p orbitals of their respective outermost shell are called p block elements.
1)A p sub shell has three degenerate p orbitals ,each one of which can accommodate 2 electrons.
2)There are 6 groups of p block elements. These are 13,14,15,16, 17and 18.
3)The atoms of the elements belonging to these groups receive the last electron in 2p, 3p, 4p, 5p and 6p orbitals.
4)Their outer shell electronic configuration vary from ns1 np6 to ns2 np6 as we move from group 13 outward upto group 18.
5)Elements of group 13, 14 ,15 ,16 ,17 ,18 in which p orbitals are being progressively filled in are called p block elements. There are 36 p-block elements in the periodic table.
6)Group 18 are called noble gases, except helium all the elements have closed shell ns2 np6 electronic configuration in the outermost shell.All the energy levels which are occupied are completely filled and this stable arrangement of electrons cannot be easily altered by addition or removal of electrons. As a result ,these elements are highly stable and hence exhibit very low chemical reactivity.
7)The elements of group 17 are called halogens while those of group 16 are called chalcogens. Elements have high negative electron gain enthalpy and hence readily add one or two electrons to attain the stable noble gas configuration.
The elements of s and p block are called representative or main group elements
General outer shell electronic configuration of d block elements: (n-1)d1-10 ns1-2
where n=4-7.
The second transition series which forms a part of the 5th period also contains 10 elements from Ytterium(Z= 39) to cadmium(Z=48) in which the 4d orbitals are being progressively filled in.
The third transition series which form a part of the sixth period also contains 10 elements i.e. lanthanum(Z=57) and from hafnium(Z=72) to mercury(Z=80) in which the 5d orbitals are the progressively filled in.
f-Block elements
The elements in which the last electron enters any one of the 7 f-orbitals of their respective ante -penultimate shell are called f block elements.
In all these element the s orbital of last shell is completely filled ,the d orbital of the penultimate(n-1) shell invariably contains 0 or one electron but the f orbital of the ante-penultimate (n-2) gets progressively filled in.
General outer shell electronic configuration of f block elements: (n-2) f 0-14 (n-1) d0-1 ns2
There are two series of f block elements each containing 14 elements. These are placed at the bottom of the periodic table.
The first 3 elements i.e. Thorium, protoactinium and uranium occur in nature but the remaining 11 elements i.e. neptunium(Z=93) to lawrencium(Z=103) have been prepared artificial through nuclear reactions.
All the f block elements i.e. lanthanides and actinides are also called inner transition elements since they form transition series within the transition elements of d- Block.