Railway Science (Chemistry-Periodic Table) (Part-VI)

Total Questions: 50

41. The first and second groups of the modern periodic table are called: [RRB Group D 5/11/2018 (Morning)]

Correct Answer: (b) S-block
Solution:

These groups include the alkali metals (Group 1) and the alkaline earth metals (Group 2). They are called the S-block elements because the outermost electron in these elements occupies the S orbital.

42. The electronic configuration of an element is 2, 8, 5. What is the name of that element? [RRB Group D 12/11/2018 (Morning)]

Correct Answer: (a) phosphorus
Solution:

phosphorus (P) has an atomic number of 15, meaning it has 15 electrons. The given configuration accurately describes the distribution of these electrons across its energy levels.
Electronic configurations: Sulphur (S₁₆): 1s² 2s² 2p⁶ 3s² 3p⁴. Chlorine (Cl₁₇): 1s² 2s² 2p⁶ 3s² 3p⁵ Magnesium (Mg₁₂): 1s² 2s² 2p⁶ 3s²

43. Which of the following always increases while moving from top to bottom in a group? [RRB Group D 12/11/2018 (Afternoon)]

Correct Answer: (a) Metallic properties
Solution:

The increase in electronegativities across a period is accompanied by an increase in non-metallic properties (or decrease in metallic properties) of elements. Electronegativity generally increases across a period from left to right (say from lithium to fluorine)and decreases down a group (say from fluorine to astatine) in the periodic table.

44. Which of the following is a property of isotopes of an element? [RRB Group D 12/11/2018 (Evening)]

(i) Their atomic masses are same.
(ii) They have the same atomic number.
(iii) They exhibit different physical properties.
(iv) They exhibit similar chemical properties.

Correct Answer: (b) (ii), (iii) and (iv)
Solution:

Isotopes have the same atomic number but different mass numbers. Examples of isotopes - Hydrogen Isotopes: Hydrogen has three naturally occurring isotopes: Protium ( ¹H), Deuterium ( ²H), and Tritium ( ³H). Carbon has two stable isotopes: Carbon-12 (¹²C) and Carbon-13 (¹³C).

45. Elements like Li, Na and K belong to _______. [RRB Group D 12/11/2018 (Evening)]

Correct Answer: (d) Alkali metal group
Solution:

Alkali metals are located in Group 1 of the periodic table. They are highly reactive metals that readily lose their outermost electron to form positively charged ions (cations) with a charge of +1. Examples of alkali metals include Rubidium (Rb), Cesium (Cs), and Francium (Fr).

46. The element, which has highest electron affinity in the third period is _________. [RRB Group D 16/11/2018 (Afternoon)]

Correct Answer: (b) Cl
Solution:

Cl : Chlorine (Atomic number 17) - It belongs to Group 17, Halogen group of the periodic table. The electron affinity is the potential energy change of the atom when an electron is added to a neutral gaseous atom to form a negative ion.

47. The electronic configuration of Al⁺³ is _________. [RRB Group D 16/11/2018 (Evening)]

Correct Answer: (a) 2,8
Solution:

Aluminum (Al) has an atomic number of 13, meaning it has 13 electrons in its neutral state. Its electronic configuration is 1s² 2s² 2p⁶ 3s² 3p¹.

48. The horizontal rows in a periodic table are called ______. [RRB Group D 26/11/2018 (Afternoon)]

Correct Answer: (d) Periods
Solution:

There are seven periods in the periodic table. Period 1 has two elements, 2nd and 3rd have 8 elements, 4th and 5th have 18 elements and 6th and 7th have 32 elements.

49. In the third period of the periodic table, the element with the smallest size is _______. [RRB Group D 26/11/2018 (Evening)]

Correct Answer: (d) CI
Solution:

CI (Chlorine). The atomic size decreases along the period towards the right but the noble gases are larger than halogens due to (Van der Wall's radius, electron configuration and the completion of electron shells in noble gases ). So the smallest element of the period is the halogen.

50. _______ is the only non-metal which exists in liquid state. [RRB Group D 1/12/2018 (Afternoon)]

Correct Answer: (a) bromine
Solution:

It is a halogen element with the atomic number 35 and is located in Group 17 of the periodic table. Mercury (Hg₈₀) is the only metal on earth that is liquid at room temperature.