Match the correct atomic radius with the element. Element Atomic radius (pm) (i) Be (a) 74 (ii) C (b) 88 (iii) B (c) 111 (iv) O (d) 77 (v) N (e) 66

Element Atomic radius (pm) (i) Be (c) 111 (ii) C (d) 77 (iii) B (b) 88 (iv) O (e) 66 (v) N (a) 74 All the given elements are of same period and along period, atomic radii decrease because effective nuclear charge increases. Thus, the order of atomic radii is O < N < C < B < Be or Be = 111 pm , O = 66 pm , C = 77 pm , B = 88 pm , N = 74 pm .

Match the correct ionisation enthalpies and electron gain enthalpies of the following elements. Elements △ H 1 △ H 2 △ eg H (i) Most reactive nonmetal (a) 419 3051 - 48 (ii) Most reactive metal (b) 1681 3374 - 328 (iii) Least reactive element (c) 738 1451 - 40 (iv) Metal forming binary halide (d) 2372 5251 + 48

Ionization enthalpy is the minimum energy required to remove an electron from an isolated neutral gaseous atom while Electron gain enthalpy is the amount of energy released when an electron added to a neutral gaseous atom. Elements △ H 1 △ H 2 △ eg H Most reactive non-metal 1681 3374 - 328 The element of (b) is the most reactive non-metal. Its electron gain enthalpy is most negative. Example: Fluorine. Elements △ H 1 △ H 2 △ eg H Most reactive metal 419 3051 - 48 The metal (a) is the most reactive metal. It has a very low value of first ionization energy. Example: Caesium(experimentally). Elements △ H 1 △ H 2 △ eg H Least reactive element 2372 5251 + 48 The element of (d) is the least reactive element as it has the highest value of first ionization energy and positive electron gain enthalpy. Example: Inert gases. The metal (c) can form a stable binary halide of the formula MX 2 as it has the lowest value of second ionization enthalpy. Elements △ H 1 △ H 2 △ eg H (i) Most reactive nonmetal (b) 1681 3374 - 328 (ii) Most reactive metal (a) 419 3051 - 48 (iii) Least reactive element (d) 2372 5251 + 48 (iv) Metal forming binary halide (c) 738 1451 - 40

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11th CBSE

IMPORTANT

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Arrange the elements $N, P, O and S$ in the order of increasing non-metallic character. Give the reason for the arrangement assigned.

Important Questions on Classification of Elements and Periodicity in Properties

HARD

11th CBSE

IMPORTANT

NCERT Exemplar Chemistry - Class 11>Chapter 3 - Classification of Elements and Periodicity in Properties>Short Answer Type>Q 38

Explain the deviation In Ionisation enthalpy of some elements from the general trend by using Figure

Question Image

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11th CBSE

IMPORTANT

NCERT Exemplar Chemistry - Class 11>Chapter 3 - Classification of Elements and Periodicity in Properties>Short Answer Type>Q 39

Explain the following:
Electronegativity of elements increases on moving from left to right in the periodic table.

MEDIUM

11th CBSE

IMPORTANT

NCERT Exemplar Chemistry - Class 11>Chapter 3 - Classification of Elements and Periodicity in Properties>Short Answer Type>Q 39

Explain the following:

Ionisation enthalpy decrease in a group from top to bottom?

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11th CBSE

IMPORTANT

NCERT Exemplar Chemistry - Class 11>Chapter 3 - Classification of Elements and Periodicity in Properties>Short Answer Type>Q 40

How does the metallic and non-metallic character vary on moving from left to right in a period?

EASY

11th CBSE

IMPORTANT

NCERT Exemplar Chemistry - Class 11>Chapter 3 - Classification of Elements and Periodicity in Properties>Short Answer Type>Q 41

The radius of

{Na}^{+}

cation is less than that of

Na

atom. Give reason.

EASY

11th CBSE

IMPORTANT

NCERT Exemplar Chemistry - Class 11>Chapter 3 - Classification of Elements and Periodicity in Properties>Short Answer Type>Q 42

Among alkali metals which element do you expect to be least electronegative and why?

MEDIUM

11th CBSE

IMPORTANT

NCERT Exemplar Chemistry - Class 11>Chapter 3 - Classification of Elements and Periodicity in Properties>Matching Type>Q 43

Match the correct atomic radius with the element.

	Element		Atomic radius (pm)
(i)	$Be$	(a)	$74$
(ii)	$C$	(b)	$88$
(iii)	$B$	(c)	$111$
(iv)	$O$	(d)	$77$
(v)	$N$	(e)	$66$

MEDIUM

11th CBSE

IMPORTANT

NCERT Exemplar Chemistry - Class 11>Chapter 3 - Classification of Elements and Periodicity in Properties>Matching Type>Q 44

Match the correct ionisation enthalpies and electron gain enthalpies of the following elements.

	Elements		$△ H_{1} △ H_{2} △_{eg} H$
(i)	Most reactive nonmetal	(a)	$419 3051 - 48$
(ii)	Most reactive metal	(b)	$1681 3374 - 328$
(iii)	Least reactive element	(c)	$738 1451 - 40$
(iv)	Metal forming binary halide	(d)	$2372 5251 + 48$

Arrange the elements N, P, O and S in the order of increasing non-metallic character. Give the reason for the arrangement assigned.

Important Questions on Classification of Elements and Periodicity in Properties

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Arrange the elements $N, P, O and S$ in the order of increasing non-metallic character. Give the reason for the arrangement assigned.