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How to find Group, Periods and Blocks of any element - (Concept)
Period
The period of any element is determined by the last shell in which the last electrons enters. For example, Fe atomic number is 26. The electronic configuration can be written as:
1s22s22p63s23p64s23d6
Now, the last electron enters into the d-subshell but electrons are also present in 4th subshell. Therefore, Fe belongs to fourth period.
Block
The block of any element is determined by the last subshell in which the last electron enters. For example, Na has atomic number 11, thus its electronic configuration can be written as:
1s22s22p63s1
Now, its last electron enters into the s-subshell, therefore, Na belongs to the s-block.
Group
The group of any element is determined in different ways.
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For s-block
If the last electron of any element enters into the s-subshell, then the group number is equal to the number of electrons in the last s-subshell.
For example, K has atomic number 19, thus its electronic configuration can be written as:
1s22s22p63s23p64s1
Now it has 1 electron in the s-subshell, therefore K belongs to Group 1.
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For p-block
If the last electron of any element enters into the p-subshell, then the group number is equal to (12 + the number of electrons in the last p-subshell).
For example, Ge has atomic number 32, thus its electronic configuration can be written as:
1s22s22p63s23p64s23d104p2
Now, it has 2 electrons in the last p-subshell, therefore its group number is:
12 + 2 = 14
Thus, Ge belongs to Group 14
- For d-block
If the last electron of any element enters into the d-subshell, then the group number is equal to (2 + the number of electrons in (n-1)d-subshell.
For example, Mn has atomic number 25, thus its electronic configuration can be written as:
1s22s22p63s23p64s23d5
Now it has 5 electrons in the d-subshell, therefore its group number is:
2 + 5 = 7
Thus, Mn belongs to Group 7.
- For f-block
There are only two series of f-block i.e, lanthanide and actinide. If the last electron of any element enters into the f-subshell and if the atomic number is between 57-71, then the element belongs to lanthanide series i.e, 6th period. Further, if the last electron of any element enters into the f-subshell and if the atomic number is between 89-103, then the element belongs to the actinide series i.e, 7th period. All the elements from both these series belong to group 3.
| Exam | Chapter |
| JEE MAIN | Classification of Elements and Periodic table |
Choose the correct option:
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The element with atomic number 35 belongs to which group:
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An element with atomic number 23 belongs to which period?
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An element of atomic number 29 belongs to
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Which pair of atomic numbers represents s-block elements
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The characteristics of elements X, Y and Z with the atomic numbers, respectively, 33,53 and 83 are:
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The elements with atomic number 101 and 104 belongs to, respectively:
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An element with atomic number 82 belongs to which group of the long form of the periodic table?
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Match List I with List II
| LIST I(Atomic Number) |
LIST II (Block of periodic table ) |
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| A. | 37 | I. | p-block |
| B. | 78 | II. | d-block |
| C. | 52 | III. | f-block |
| D. | 65 | IV | s-block |
Choose the correct answer from the options given below:
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Which of the following sets contain only isoelectronic ions?
(i) $\mathrm{Zn}^{2+}, \mathrm{Ca}^{2+}, \mathrm{Ga}^{3+}, \mathrm{Al}^{3+}$
(ii) $\mathrm{K}^{+}, \mathrm{Ca}^{2+}, \mathrm{Sc}^{3+}, \mathrm{Cl}^{-}$
(iii) $\mathrm{P}^{-3}, \mathrm{~S}^{2-}, \mathrm{Cl}^{-}, \mathrm{K}^{+}$
(iv) $\mathrm{Ti}^{4+}, \mathrm{Ar}, \mathrm{Cr}^{3+}, V^{5+}$
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The element with atomic number 16 belongs to which group of the periodic table:
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The element with the electronic configuration $[X e] 4 f^{14} 5 d^1 6 s^2$ belongs to which of the following group:
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The penetration effect of the orbitals the correct order is
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An element has the configuration $1 s^2, 2 s^2, 2 p^6, 3 s^2, 3 p^2$ : To which block in the long form of the periodic table, does this belong?
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A modern version, the so-called “long form” of the Periodic Table of the elements (Fig. 3.2), is the most convenient and widely used. The horizontal rows (which Mendeleev called series) are called periods and the vertical columns, groups. Elements having similar outer electronic configurations in their atoms are arranged in vertical columns, referred to as groups or families.
