In Modern periodic table, elements are arranged in the order of increasing atomic numbers. Here we will discuss the classification of Modern periodic table.

What is Modern periodic table

Modern P.T. has another name called long form of periodic table. It has 18 groups, 7 periods and 4 blocks.

How many periods are present in Modern P.T.

1. First period has 2 elements: H, He. It is the shortest period in the periodic table.
2. Second period has 8 elements. It is the short period. It has elements from Li to Ne ( At. No. – 3 to At. No. – 10 )
3. Third period has 8 elements. It is the short period. It has elements from Na to Ar ( At. No. – 11 to At. No. – 18 )
4. Fourth period has 18 elements. It has elements involving the filling of 4s, 3d and 4p orbitals. It is a long period.
5. Fifth period has 18 elements. It has elements involving the filling of 5s, 4d and 5p orbitals. It is a long period.
6. Sixth period has 32 elements. It has elements involving the filling of 6s, 4f, 5d & 6p orbitals. It is a longest period.
7. Seventh period has 32 elements. It has elements involving the filling of 7s, 5f, 6d & 7p orbitals. It is a longest period.

How many blocks are present in Modern P.T.

There are 4 blocks present in the long form of periodic table.

s-block elements

1. It includes group 1 and group 2.
2. These elements contain 1 (alkali metals ) or 2 (alkaline earth metals) electrons in the s orbital of the outermost shell.
3. The electronic configuration of s block elements is ns^1-2
4. There are 14 s block elements in the periodic table.

p-block elements

1. It includes from group 13 to group 18
2. These elements contain 1-6 electrons in the p orbital of the outermost shell.
3. The electronic configuration of s block elements is ns²np^1-6
4. There are 36 p block elements in the periodic table.

d-block elements

1. It includes from group 3 to group 12
2. The first transition series, 3d series involves filling of 10 elements ( ₂₁Sc-₃₀Zn)
3. Second transition series, 4d series involves filling of 10 elements (₃₉Y-₄₈Cd)
4. Third transition series, 5d series involves filling of 10 elements (₇₂Hf-₈₀Hg and ₅₇La)
5. Fourth transition series 6d series involves filling of 10 elements from ₁₀4Rf-₁₁₂Cn and ₈₉Ac)
6. There are 40 d block elements in the periodic table.

f-block elements

1. These include inner transition elements contain 1-14electrons in the f-orbitals of the anti-penultimate shell.
2. The general outer electronic configuration is (n-2)f^1-14(n-1)d^0-1ns² where n= 6-7
3. There are 2 series of f block elements each containing 14 elements.
4. 4f series, lanthanides series are having 14 elements ₅₈Ce-₇₁Lu (rare earth elements)
5. 5f series, actinides series are having 14 elements ₉₀Th-₁₀₃Lr
6. All actinides are radioactive elements.
7. First 3 actinides elements occur in nature but rest are artificially prepared through nuclear reactions.

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