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

Total Questions: 50

1. Which of the following oxides corresponds to the oxide of Eka-aluminum? [RRC Group D 12/09/2022 (Afternoon)]

Correct Answer: (a) πΊπ‘Žβ‚‚ 𝑂₃
Solution:

Aluminium Oxide (Alβ‚‚O₃). While forming the periodic table, Mendeleev left few spaces for the elements yet to be discovered whose properties were predicted by him. He named them with the prefix "Eka" followed by the element showing closest similarity in its properties.

2. Which shell of the nitrogen atom participates in forming Nβ‚‚ molecule? [RRC Group D 12/09/2022 (Afternoon)]

Correct Answer: (d) L
Solution:

Nitrogen: p-block element. Atomic number - 7. Electronic configuration: N→1s²2s²2p³ . Orbit - K (total number of electrons - 2), L (8), M (18), N (32). Uses - make fertilisers, nitric acid, nylon, dyes and explosives. Liquid nitrogen - Used as a refrigerant in the transportation and freezing of food.

3. Which statement is correct for the elements of the second period? [RRC Group D 12/09/2022 (Afternoon)]

Correct Answer: (b) They do not have the same number of valence electrons, but they contain the same number of shells.
Solution:

Second Period Elements - lithium(Li), beryllium(Be), boron(B), carbon(C), nitrogen(N), oxygen(O), fluorine(F), and neon(Ne).
Properties - atomic number increases, atomic radius of the elements decreases, electronegativity increases and the ionization energy increases.

4. In Mendeleev's Periodic Table, at which position are the formulae of hydrides and oxides of elements written? [RRC Group D 12/09/2022 (Evening)]

Correct Answer: (b) Top
Solution:

Mendeleev concentrated on the compounds formed by the elements with Hydrogen and Oxygen. Hydrogen and Oxygen are highly reactive and hence formed compounds with almost all the elements. Mendeleev classified all the 63 elements discovered in 1872 in Mendeleev’s periodic table based on the increasing order of their atomic mass and the formula of their hydrides and oxides. Hydrogen was kept in Group (1) the only element in the first period. The second period had Li, Be, B, C, N, O, F. Modern periodic table consists of 18 groups and 7 periods.

5. Which of the following elements of group 14 is a metalloid? [RRC Group D 13/09/2022 (Morning)]

Correct Answer: (a) Ge
Solution:

The group 14 elements (electronic configuration is nsΒ²npΒ² ) are the second group in the p-block of the periodic table called the carbon group. Group 14 elements - Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn), Lead (Pb), Flerovium (Fl).
Two metalloids - Silicon (Si) and Germanium. Non-metals - Carbon (C) and Silicon (Si). Soft metals (low melting points) - Tin (Sn) and Lead (Pb).

6. Which of the following elements is a metalloid? [RRC Group D 13/09/2022 (Evening)]

Correct Answer: (c) Antimon
Solution:

Antimony (Sb), Group 15, Atomic Number 51. Other metalloids- boron (B, 5), silicon (Si, 14), germanium (Ge, 32), arsenic (As, 33), tellurium (Te, 52) and astatine (At, 85). Bismuth (Bi, 83). Iron (Fe, 26).

7. Which of the following elements has three shells with two valence electrons? [RRC Group D 14/09/2022 (Afternoon)]

Correct Answer: (c) Mg
Solution:

Cl (Chlorine): Atomic Number- 17. Uses - Disinfect water, Sanitation process of industrial waste etc. Si (Silicon, 14 ). Uses - Making transistors, Computer chips and Solar cells, Portland cement, etc. P (Phosphorus, 15).
Uses - formation of bones and teeth, manufacture of safety matches (red phosphorus), pyrotechnics and incendiary shells.

8. Which of the following metals is the most reactive? [RRC Group D 14/09/2022 (Afternoon)]

Correct Answer: (a) Mg
Solution:

(Magnesium): Atomic Number- 12, Uses - Magnesium and its alloys have very good corrosion resistance and good high temperature mechanical properties. The metal reacts with water to produce hydrogen gas.
Most Reactive metal decreasing order K (Potassium), Na (Sodium), Ca (Calcium), Mg (Magnesium), Al (Aluminium), C (carbon), Zn (Zinc), Sn (Tin), Fe (Iron), Pb (Lead), H (Hydrogen), Cu (copper), Ag (Silver), Au (Gold), Pt (Platinum).

9. What are the group numbers of halogens and carbon family, respectively, in the modern periodic table? [RRC Group D 14/09/2022 (Evening)]

Correct Answer: (b) Group 17 and Group 14
Solution:

Halogens (salt former) elements - Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At). Properties - low melting and boiling points, high electronegativities, sparingly soluble in water. Carbon Group - Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn), and Lead (Pb). Properties - less electropositive than group 13 owing to their small size and high ionization enthalpy.

10. Which statement about Mendeleev's Periodic Table is INCORRECT? [RRC Group D 15/09/2022 (Afternoon)]

Correct Answer: (b) The properties of elements are the periodic functions of their atomic numbers.
Solution:

Dmitri Ivanovich Mendeleev’s Periodic Table (1869): The properties of elements are the periodic functions of their atomic mass. It had 8 groups and 7 periods, and Total number of elements was 63.