Chemistry (Part-III)

1. Halogens have _________ electrons in their outer-most shells. [S.S.C. Online CGL (T-I) 16.08.2021]

(a) Eight
(b) Seven
(c) Five
(d) Six

Correct Answer: (b) Seven

Solution:Halogens are elements in Group 17 of the periodic table. They have Seven electrons in their outermost shells. This electron configuration (ns²np⁵) is one electron short of a stable noble gas configuration.

2. The elements of groups 3 to 12 are called __________ elements or transition elements. [S.S.C. Online Graduate Level (T-I) 16.08.2021]

(a) c-block
(b) d-block
(c) b-block
(d) a-block

Correct Answer: (b) d-block

Solution:Elements in groups 3 to 12 of the periodic table are called d-block elements or transition clements. The d-orbitals of these elements are incomplete or only partially complete. All transition elements are metals.

3. The elements in the middle of the periodic table are called __________. [S.S.C. Online MTS (T-I) 10.10.2017]

(a) Metalloids
(b) Transition element
(c) Rare carth element
(d) Noble gas

Correct Answer: (b) Transition element

Solution:Elements found in the middle part of the periodic table are called 'transition elements. They are called d-block elements because the electrons added to this block of elements are added to the
d-orbital.

4. Elements in a period have same: [S.S.C. Ane MTS (T-I) 12.10.2017]

(a) Number of valence electrons
(b) Valency
(c) Number of shells
(d) Volume

Correct Answer: (c) Number of shells

Solution:

Elements in a period (horizontal row) have the same Number of shells. As you move across a period, electrons are added to the same principal energy level (shell).

5. Which of the following elements is NOT a Rare Earth Element? [S.S.C. JE Civil Exam 30.10.2020]

(a) Helium
(b) Cerium
(c) Lanthanum
(d) Praseodymium

Correct Answer: (a) Helium

Solution:Rare Earth Elements consist of the Lanthanoids (atomic numbers 57-71) and the Actinoids (atomic numbers 89-103). Among the options, Helium is a noble gas and is NOT a Rare Earth Element. Cerium, Lanthanum, and Praseodymium are Lanthanoids.

6. Which of the following metals has maximum thermal conductivity? [S.S.C. Online Graduate Level (T-I) 4.09.2016]

(a) Iron
(b) Silver
(c) Aluminium
(d) Copper

Correct Answer: (b) Silver

Solution:When a metal is heated, its atoms gain energy and vibrate more vigorously. This energy is transferred to the electrons present in the atoms. These electrons travel to the metal, they transfer energy to other electrons and atoms of the same element. The thermal conductivity is represented by the sign K. The thermal conductivity of metals generally decreases with increasing temperature. Among the given options, Silver has the highest thermal conductivity.

7. Which of the following is a polar molecule? [S.S.C. Online C.H.S.L. (T-I) 09.08.2021]

(a) Carbon dioxide
(b) Water
(c) Carbon tetrachloride
(d) Benzene

Correct Answer: (b) Water

Solution:Water molecules (H₂O) are polar in nature. That is both the hydrogen atoms present in a molecule of water have a positive charge and the central oxygen atom has a negative charge. This is due to oxygen's more negatively electronegative nature, which results in higher electron density near the oxygen atom.
Water (H₂O) has a bent geometry, and the polar O-H bonds result in a net dipole moment, making it a polar molecule.

8. In reference to atomicity, argon is: [S.S.C. Online CGL (T-I) 20.08.2021]

(a) monoatomic
(b) diatomic
(c) triatomic
(d) polyatomic

Correct Answer: (a) monoatomic

Solution:

Atomicity refers to the number of atoms in a molecule of an element. Argon (Ar) is a noble gas and exists as single, unbonded atoms. Therefore, argon is monoatomic.

9. Which is the heaviest metal among the following? [S.S.C. Online Graduate Level (T-I) 1.09.2016]

(a) Gold
(b) Silver
(c) Iron
(d) Copper

Correct Answer: (a) Gold

Solution:Those elements whose density is more than 5 grams per cubic centimeter are called 'heavy metals". The density of gold is 19.32, the density of silver is 10.5. the density of iron is 7.87 and that of copper is 8.96. Hence, the heaviest metal among the above is gold.

10. Which one of the following elements is a Monatomic unit? [S.S.C. Online CGL (T-I) 17.08.2021]

(a) Gold
(b) Phosphorus
(c) Sulphur
(d) Hydrogen