268. In the modern periodic table, elements are arranged in order of increasing atomic numbers which is related to the electronic configuration. Depending upon the type of orbitals receiving the last electron, the elements in the periodic table have been divided into four blocks, viz, s, p, d, and f; The modern periodic table consists of 7 periods and 18 groups. Each period begins with the filling of a new energy shell. In accordance with the Aufbau principle, the seven periods (1 to 7) have 2, 8, 8, 18, 18, 32, and 32 elements respectively. The seventh period is still incomplete. To avoid the periodic table being too long, the two series off-block elements, are called. lanthanoids and actinoids are placed at the bottom of the main body of the periodic table.
The element with atomic number 57 belongs to

s - block

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p - block

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d - block

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f - block

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Solution

The correct option is C
d - block

The element with atomic number 57 is lanthanum $(La)$ .
Lanthanum has electronic configuration (1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²5d¹).
Therefore, it is a member of d-block elements as the last valence electron enters d orbital.
The d- block elements are called transition elements and have valence electrons in the d-orbital that's why such metals are named as d-block elements.
Lanthanum belongs to 5d transition element series.
Hence, option (C) is correct.

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Similar questions

(i) Comprehension given below is followed by some multiple choice questions. Each question has one correct option. Choose the correct option. In the modern periodic table, elements are arranged in order of increasing atomic numbers which is related to the electronic configuration. Depending upon the type of orbitals receiving the last electron, the elements in the periodic table have been divided into four blocks, viz s, p, d, and f.
The modern periodic table consists of 7 periods and 18 groups. Each period begins with the filling of a new energy shell. In accordance with the Aufbau principle, the seven periods (1 to 7 ) have 2, 8, 8, 18, 18, 32, and 32 elements respectively.
The seventh period is still incomplete. To avoid the periodic table being too long , the two series of f-block elements, called lanthanoids and actionoids are placed at the bottom of the main body of hte periodic table
The element with atomic number 57 belongs to
(a) s- block ( b) p-block (c) d- block (d) f- block

(ii) The last element of the p - block in 6th period is represented by the outermost electronic configuration.
(a) $7 s^{2} 7 p^{6}$ (b) $5 f^{14} 6 d^{10} 7 s^{2} 7 p^{0}$
(c) $4 f^{14} 5 d^{10} 6 s^{2} 6 p^{6}$ (d) $4 f^{14} 5 d^{10} 6 s^{2} 6 p^{4}$

(iii) Which of the elements whose atomic numbers are given below, cannot be accommodated in the present set up of the long frm of the periodic table?
(a) 107 (b) 118 (c) 126 (d) 102

(iv) The electronic configuration of the element which is just above the element with atomic number 43 in the same group is .....
(a) $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{5} 4 s^{2}$
(b) $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{5} 4 s^{3} 4 p^{6}$
(c) $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{6} 4 s^{2}$
(d) $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 3 d^{7} 4 s^{2}$

(v) The elements with atomic numbers 35, 53 and 85 are all ..
(a) noble gases (b) halogens (c) heavy metals (d) light metals

Q. (a) What were the two major shortcomings of Mendeleev's periodic table? How have these been removed in the modern periodic table?
(b) Two elements X and Y have atomic numbers 12 and 16 respectively. Write the electronic configuration for these elements. To which period of the modern periodic table do these two elements belong? What type of bond will be formed between them and why?
(c) To which groups of the modern periodic table do the elements X and Y belong? Give reason for your answer.
(d) What could the elements X and Y be? Write their names and symbols.

(a) State modern periodic law.

(b) How does the electronic configuration of the atom of an element relate to its position in the modern periodic table?

(d) Is it possible to have an element having atomic number 1.5 placed between hydrogen and helium?

(e) Name the scientist who prepared the modern periodic table.

Which of the following statements (s) about the Modern Periodic table are incorrect?

(i) The elements in the Modern Periodic Table are arranged on the basis of their decreasing atomic numbers.

(ii) The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic masses.

(iii) Isotopes are placed in adjoining group (s) in the periodic table.

(iv) The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic numbers.

Q. Which of the following statement is correct in regard to the classification of elements?

(a) Elements in modern periodic table are arranged on the basis of increasing atomic masses.
(b) Elements in Mendeleev's periodic table are arranged on the basis of increasing atomic numbers.
(c) In modern periodic table, the element nickel of lower atomic mass is kept before the element cobalt of higher atomic mass.
(d) In modern periodic table, the isotopes of chlorine having different atomic masses are kept in the same group.

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