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Classification of Elements and Periodicity in Properties

Short Answer Type

131.

Nitrogen and phosphorus have high value of ionisation enthalpies. Explain.

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132.

Be and Mg have high value of ionisation enthalpies. Explain.

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133. Would you expect the first ionization enthalpies for two isotopes of the same element to be the same or different? Justify your answer.

158 Views

Long Answer Type

134.

Which of the following pairs of elements would you expect to have lower first ionisation enthalpy? Explain your answer:

(a) Cl or F

(b) Cl or S

(c) K or Ar

(d) Kr or Xe.

294 Views

Short Answer Type

135.

Among the elements of second period i.e. from Li to Ne, pick out the elements:

(a) with the highest first ionisation enthalpy
(b) with the highest electronegativity
(c) with the largest atomic radius
(d) which is the most reactive non-metal
(e) which is the most reactive metal ?

1100 Views

136.

The first (IE₁) and second (IE₂) ionisation enthalpies (kJ mol^-1) of a few elements by Roman numerals are as shown:

	IE₁	IE₂
i	2372	IE₂
ii	520	7300
iii	900	1760
iv	1680	380

which of the above elements is likely to be:
(i) a reactive metal
(ii) a reactive non-metal
(iii) a noble gas
(iv) a metal that forms a stable binary halide of the formula AX₃ (X = halogen).

183 Views

Long Answer Type

137.

The IE₁, of carbon, is more than that of boron while its IE₂ value is smaller. Explain.

143 Views

Short Answer Type

138.

Arrange the following in order of increasing ionisation enthalpies and assign reason:

(i) K⁺, Ar, Cl^-(ii) Fe, Fe²⁺, Fe³⁺

200 Views

139.
How would you explain the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium?

The electronic configurations of Na and Mg are:
₁₁Na ; 1s²2s²2p⁶3s^1.
₁₂Mg : 1s²2s²2p⁶3s²The first ionization enthalpy of sodium is lower than that of magnesium because the nuclear charge of Na (+11) is lower than that of Mg (+12) and size of Na is lower than Mg. After the loss of first electron, the electronic configuration of Na⁺ is 1s²2s¹2p⁶ (has noble gas configuration) and Mg⁺is 1s²2s²2p⁶3s¹. Hence removal of the second electron from Na⁺ is very difficult as compared to Mg⁺(electron to be removed from 3s). Thus second ionisation enthalpy of sodium is higher than that of magnesium.

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140.

The first ionization enthalpy values (in kJ mol^-1) of group 13 elements are:
B Al Ga In Tl
801 577 579 558 589
How would you explain this deviation from the general trend?

159 Views