Q14 of 59 Page 30

In the following questions two or more options may be correct.

Which of the following elements can show covalency greater than 4?


Vacant d-orbitals in elements allows transfer of electrons after unpairing electrons from s and p orbitals. D- orbitals are present in P and S due to which they can accommodate extra electrons which increases their covalency.

In excited state sulphur has a valency of six due to six unpaired electrons. Similarly in phosphorous it has a valency of 5 in the excited state due to the presence of the 5 unpaired electrons.


For example,


Sulphur configuration: 1s2 2s2 2p6 3s2 3p4


Sulphur configuration excited state: 1s2 2s2 2p63s13p33d2


Phosphorous configuration: 1s2 2s2 2p6 3s2 3p3


Phosphorous configuration excited state: 1s2 2s2 2p63s1 3p33d1

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12 E

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 Arfbau 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 actinoids are placed at the bottom of the main body of the periodic table.


The elements with atomic numbers 35, 53 and 85 are all ________.


 13

Electronic configurations of four elements A, B, C and D are given below :

(A) 1s2 2s2 2p6


(B) 1s2 2s2 2p4


(C) 1s2 2s2 2p6 3s1


(D) 1s2 2s2 2p5


Which of the following is the correct order of increasing tendency to gain electron :


 15

In the following questions two or more options may be correct.

Those elements impart colour to the flame on heating in it, the atoms of which require low energy for the ionisation (i.e., absorb energy in the visible region of spectrum). The elements of which of the following groups will impart colour to the flame?


 16

In the following questions two or more options may be correct.

Which of the following sequences contain atomic numbers of only representative elements?