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Previous Year Questions Of Periodic Classification of Elements

Previous Year Questions Of Periodic Classification of Elements

Q 2704101058

Which one of the following elements is least reactive with water ?
NDA Paper 2 2017
(A)

Lithium

(B)

Sodium

(C)

Potassium

(D)

Cesium

Solution:

Correct Answer is `=>` (D) Cesium
Q 2714501459

Radon is
NDA Paper 2 2017
(A)

an inert gas

(B)

an artificial fibre

(C)

an explosive

(D)

a metal

Solution:

Correct Answer is `=>` (A) an inert gas
Q 2262167035

The alkali metals have relatively low melting point. Which one of the following alkali metals is expected to have the highest melting point?
NDA Paper 2 2015
(A)

Li

(B)

Na

(C)

K

(D)

Rb

Solution:

On moving from Li to Cs, size of atom increases so interatomic interaction becomes weak resulting in low melting point. Among alkali metals, Li have the highest melting point.
Correct Answer is `=>` (A) Li
Q 2306191078

Two reactants in a flask produce bubbles of gas, it turns limewater into milky The reactants in the flask are
NDA Paper 2 2013
(A)

zinc and hydrochloric acid

(B)

magnesium carbonate and hydrochloric acid

(C)

magnesium nitrate and hydrochloric acid

(D)

magnesium sulphate and hydrochloric acid

Solution:

The reactant in the flash are magnesium carbonate and hydrochloric acid. the reaction is

`MgCO_3(s) + 2HCl(aq) -> MgCl_2(aq) + CO_2(g) + H_2O (l)`
Correct Answer is `=>` (B) magnesium carbonate and hydrochloric acid
Q 2317145989

Which one among the following does not have an allotrope?
NDA Paper 2 2012
(A)

Oxygen

(B)

Sulphur

(C)

Nitrogen

(D)

Carbon

Solution:

Nitrogen is a chemical element with symbol N and atomic number 7. Elemental nitrogen is a colourless, odourless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.09% by volume of Earth's atmosphere. The element nitrogen was discovered as a separable component of air, by Scottish physician Daniel Rutherford, in 1772. It does not have any allotrope.
Correct Answer is `=>` (C) Nitrogen
Q 2318612500

Which one of the following is a transition metal ?
NDA Paper 2 2010
(A)

Aluminium (AI)

(B)

Manganese (Mn)

(C)

Magnesium (Mg)

(D)

Calcium (Ca)

Solution:

In transition metals, the last electron enters in penultimate shell. The electronic configuration of the given metals is as

`text()_13 Al=2,8,3`

`text()_25 Mn=2,.8,13,2`

`text()_12 Mg=2,8,2`

`text()_20Ca=2,8,2`

Electronic configurations reveal that it is only Mn, in which the last electron enters in penultimate shell. Thus, Mn (manganese) is a transition element (or metal).
Correct Answer is `=>` (B) Manganese (Mn)
Q 2387223187

Which one of the following elements exists in liquid state at room temperature?
NDA Paper 2 2009
(A)

Mercury

(B)

Lead

(C)

Sodium

(D)

Calcium

Solution:

Most of the metals like iron, lead, sodium, calcium, copper, silver etc, are solids at the room temperature. Only mercury metal is found in liquid state at the room temperature.
Correct Answer is `=>` (A) Mercury
Q 2317067880

When an alkali metal reacts with water, which one of the following gases is produced?
NDA Paper 2 2008
(A)

Hydrogen

(B)

Oxygen

(C)

Hydrogen peroxide

(D)

Ozone

Solution:

Alkali metals react with water to produce hydrogen gas

`2Na+2H_2O-> 2NaOH+H_2 uparrow`
Correct Answer is `=>` (A) Hydrogen
Q 2307167988

In which one of the following is the valence electronic configuration, `ns^2 np^3` found?
NDA Paper 2 2008
(A)

Carbon

(B)

Oxygen

(C)

Nitrogen

(D)

Argon

Solution:

The configuration `ns^ 2, np^3` is of `15` or VA group of the periodic table and nitrogen belongs to `15` or VA group, so it is found in nitrogen.

`text()_7 N=underbrace(1s^2,2s^2,2p^3)`
Correct Answer is `=>` (C) Nitrogen
Q 2367578485

What is the correct increasing order of electronegativity for the most common oxidation states among the following elements?
NDA Paper 2 2007
(A)

`F < O < N < C`

(B)

`O < N < C < F`

(C)

`C < N < F < O`

(D)

`C < N < O < F`

Solution:

On moving across a period left to right the value of electronegativity increases. Hence, the increasing order of electronegativity is as

`C < N < O < F`
Correct Answer is `=>` (D) `C < N < O < F`
Q 2317280180

At `30°C`, which three metals are all liquids?
NDA Paper 2 2007
(A)

`Hg, Fe, Zn`

(B)

`Hg, Sn, Pb`

(C)

`Zn, Pb, Sn`

(D)

`Hg, Ga, Cs`

Solution:

At room temperature `(30^oC) Hg, Ga, Cs` metals are
liquids
Correct Answer is `=>` (D) `Hg, Ga, Cs`
Q 2347280183

Which one of the following noble gases is not found in the atmosphere'?
NDA Paper 2 2007
(A)

Argon

(B)

Krypton

(C)

Radon

(D)

Xenon

Solution:

Radon (Rn) is radioactive and does not occur in the free state because it decays very rapidly. It is not present in atmosphere. While other noble gases (`He, Ar, Ne, Kr, Xe`) are found in atmosphere in their atomic state.
Correct Answer is `=>` (C) Radon
 
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