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

Total Questions: 49

11. M (orbit) shell can accommodate _____ electrons. [RRB Group D 12/12/2018 (Morning)]

Correct Answer: (a) 18
Solution:

The maximum number of electrons present in a shell is given by the formula 2n² (n = orbit number). The maximum number of electrons that can be filled in the shell K, L, M, N respectively are 2, 8, 18, 32.

12. In a group, the number of valence electrons is _______. [RRB Group D 12/12/2018 (Afternoon)]

Correct Answer: (a) remains the same
Solution:

Valence electrons are the electrons found in the outermost shell of an atom. These electrons are involved in chemical bonding and determine the chemical properties of an element. For example, Group 1 elements (such as Hydrogen, Lithium, Sodium) all have one valence electron.

13. Name the element whose electronic configuration is 2, 8 and 6. [RRB Group D 13/12/2018 (Morning)]

Correct Answer: (b) Sulphur
Solution:

Beryllium: Atomic number - 4, Electron configuration: [He] 2s². Potassium (K): Atomic number - 19, Electron configuration - [Ar] 4s¹. Fluorine: Atomic number - 9. Electron configuration - [He] 2s²2p⁵.

14. Silicon forms a compound with hydrogen consisting of a chain of _______ atoms. [RRB Group D 14/12/2018 (Afternoon)]

Correct Answer: (b) 7 or 8
Solution:

But, these compounds are highly reactive. This is because silicon has a larger atomic radius and lower electronegativity than carbon, which makes the Si−H bonds weaker and more prone to hydrolysis. These compounds are called silanes, and they are analogues of alkanes in organic chemistry.

15. Which of the following is the last element in Newlands Law of Octaves classification? [RRB ALP Tier - I (09/08/2018) Morning]

Correct Answer: (c) Thorium
Solution:

Thorium (Th): Atomic number 90. 56 known elements were arranged by Newland in the order of increasing atomic masses in 1864. He observed that the properties of every eighth element are similar to the properties of the first element. First element- Hydrogen (H). Example: Sodium (Na,11) having the similar properties to lithium (Li, 3). Elements and Atomic number: Radium (Ra, 88), Iron (Fe, 26) and Rhodium (Rh, 45).

16. Elements A, B and C occur as Dobereiner's triads. If the atomic mass of A is 7 and that of C is 39, what will be the atomic mass of B? [RRB ALP Tier - I (09/08/2018) Morning]

Correct Answer: (b) 23
Solution:

Dobereiner's law of triads - The atomic mass of the middle element of a triad is the arithmetic mean of the atomic masses of the other two elements. He identified 3 triads - 1st {Lithium (Li), Sodium (Na), Potassium (K)}, 2nd {Calcium (Ca), Strontium (Sr), Barium (Ba)}, 3rd {Chlorine (Cl), Bromine (Br), Iodine (I)}. Given, Atomic mass of A = 7 , Atomic mass of C = 39.

17. What happens as we go down the group in the periodic table? [RRB ALP Tier - I (09/08/2018) Evening]

Correct Answer: (c) The number of shells increases
Solution:

Go top to bottom of a group in the periodic table: Size of atom (increases), electronegativity (decreases), Electron affinity (decreases). Left to right across a period: Size of atom (decreases), electronegativity (increases), number of valence electrons (increases), and Electron affinity (increases).

18. Among chemical properties, Mendeleev concentrated on the compounds formed by the elements with: (Periodic Table) [RRB ALP Tier - I (10/08/2018) Morning]

Correct Answer: (a) Hydrogen and Oxygen
Solution:

They are highly reactive and hence formed compounds with almost all the elements. Dmitri Mendeleev - The father of the Periodic Table. Periodic laws - The properties of elements are the periodic function of their atomic mass.

19. Which one of the following is not a borderline element [RRB ALP Tier - I (10/08/2018) Afternoon]

Correct Answer: (c) Bismuth
Solution:

Atomic number - 83. Metalloids are termed as the borderline elements, as they possess the properties of both metals and nonmetals and form a borderline between the two. Examples - Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), Polonium (Po) and Astatine (At).

20. What are transition elements? [RRB ALP Tier - I (10/08/2018) Afternoon]

Correct Answer: (d) Elements whose two outermost shells are incomplete
Solution:

Transition elements - Those elements whose two outermost shells are incomplete. According to IUPAC (International Union of Pure and Applied Chemistry), an element having d sub-shell that is partially filled or any element which can form stable cations with an incompletely filled d orbital. Elements in the d - block in the modern periodic table come under transition elements. Example - Copper(Cu), Iron (Fe), Nickel (Ni).