Question

Write an essay on s, p, d, f block elements.

Answer 1

Hint: Elements are classified into groups as s-block, p-block, d-block, and f-block elements depending upon the type of orbitals that are being filled with electrons. Helium and hydrogen are exceptions from this categorisation.

Complete step by step answer:
You can see in the periodic table elements are divided into s-block, p-block, d-block, and f-block elements. This classification is based on the type of atomic orbitals that are being filled by the electrons.
s-block elements: Group 1 (alkali metals) and group 2 (alkaline earth metals) elements have $n{s}^1$ and $n{s}^2$ electronic configuration respectively, therefore called s- block elements. They all are reactive metals with low ionization energies. They lose their outermost electron(s) readily to form +1 ion (in case of group 1 elements) and +2 (in case of group 2 elements). The metallic character increases down the group.
p-block elements: The p-block elements comprises group 13 to 18 elements. The outermost electronic configuration varies from $n{s}^{2}n{p}^1$ to $n{s}^{2}n{p}^6$ in each period. At the end of each period is a noble gas element with a complete valence shell $n{s}^{2}n{p}^6$configuration. The elements in the end group 17 in the p-block are called halogens. The non-metallic character increases as we move across a period from left to right and metallic character increases down the group.
d-block elements (transition elements): Elements of group 3 to 12 in the centre of the periodic table are d-block elements, also called as transition elements. These are called d-block elements because of the filling of inner d-orbitals by electrons. These elements have general electronic configuration: $(n-1)d^{1-10}n{s}^{0-2}$. They are all metals. They mostly form coloured ions, show variable oxidation states, paramagnetism and also used as catalysts.
f-block elements (Inner-transition elements): The two rows at the bottom of the periodic table, called Lanthanides (Ce to Lu) and Actinoids (Th to Lr), have the electronic configuration $(n-2)f^{1-14}(n-1)d^{0-1}n{s}^2$. In f-block elements, the last electron is filled in the f-orbital. These two series of elements are also called inner-transition elements. Within each series, the properties of elements are quite similar. Actinoid elements are generally radioactive.

Note: We notice two exceptions in the periodic table. The one is hydrogen which has only one s-electron and hence can be placed in group 1. It can also gain an electron to achieve noble gas configuration and hence can behave as group 17 elements also. As it is a special case, we place hydrogen at the top of the periodic table. The other exception is helium, which belongs to the s-block but its positioning in the p-block with group 18 elements is justified because it has a completely filled valence shell and thus is an inert gas.