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Classification of Elements and Periodicity in Properties

Multiple Choice Questions

The electronic configuration of Eu (Atomic no.63), Gd (Atomic no. 64) and Tb (Atomic no. 65) are

[Xe]4f⁶ 5d¹ 6s², [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁹ 6s²
[Xe] 4f⁶ 5d¹ 6s² , [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁸ 5d¹ 6s²
[Xe] 4f⁷ 6s², [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁹ 6s²
[Xe] 4f⁷ 6s², [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁹ 6s²

1993 Views

2.
In which of the following options the order of arrangement does not agree with the variation of the property indicated against it?

B<C<N<O (increasing first ionisation enthalpy)

I<Br<Cl<F(increasing electron gain enthalpy)

Li<Na<K<Rb (increasing metallic radius)

Li<Na<K<Rb (increasing metallic radius)

I<Br<Cl<F(increasing electron gain enthalpy)

The electron gain enthalpy is defined as the energy released when an electron is added to a neutral gaseous atom to convert it into a negative ion. Large negative values of electron gain enthalpy indicate that it is easier to add an electron to an atom to convert it into an anion, and hence large amount of energy is released. The electron gain enthalpies in halogens decreases in the order
Cl>F>Br>I

because as we proceed down a group because the size of the atom increases. Therefore the distance of the nucleus from the valence orbital (which accepts the additional electron) increases. Hence the force by which the additional electron is attracted by the nucleus also decreases and the electron gain enthalpies become less negative as we proceed down a group.

1124 Views

The species Ar, K⁺ and Ca²⁺ contain the same number of electrons. In which order do their radii increase?

Ar < K⁺< Ca²⁺
Ca²⁺ < Ar < K⁺
Ca²⁺ < K⁺ < Ar
Ca²⁺ < K⁺ < Ar

1221 Views

Solubility of the alkaline earth's metal sulphates in water decreases in the sequence

Mg>Ca>Sr>Ba
Ca>Sr>Ba>Mg>
Sr>Ca>Mg>Ba
Sr>Ca>Mg>Ba

734 Views

Which of the following pairs of ions are isoelectronic and isostructural?

$CO subscript 3 superscript 2 minus end superscript comma space SO subscript 3 superscript 2 minus end superscript$
$ClO subscript 3 superscript minus comma space CO subscript 3 superscript 2 minus end superscript$
$SO subscript 3 superscript 2 minus end superscript comma NO subscript 3 superscript minus$
$SO subscript 3 superscript 2 minus end superscript comma NO subscript 3 superscript minus$

2058 Views

The number of d- electrons in Fe²⁺ (Z = 26) is not equal to the number of electrons in which one of the following?

S- electronic in Mg (Z=12)
p-electrons in Cl( Z=17)
d- electrons in Fe (Z=26)
d- electrons in Fe (Z=26)

984 Views

which of the following orders of ionic radii is correctly represented?

H^- > H >H⁺
Na⁺ >F^- >O^2-
F^- > O^2->Na⁺
F^- > O^2->Na⁺

1051 Views

Be²⁺ is isoelectronic with which of the following ions?

H⁺
Li⁺
Na⁺
Na⁺

2186 Views

Identify the wrong statement in the following.

Amongst isoelectronic species, smaller the positive charge on the cation, smaller is the ionic radius
Amongst isoelectronic species, greater the negative charge on the anion, larger is the ionic radius
Atomic radius of the elements increases as one moves down the first group of the periodic table
Atomic radius of the elements increases as one moves down the first group of the periodic table

890 Views

10.

Which of the following represents the correct order of increasing electron gain enthalpy with negative sign for the elements O, S, F and Cl?

Cl < F < O < S
O < S < F< Cl
F < S < O < Cl
F < S < O < Cl

812 Views