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

Total Questions: 50

31. Which of the following statements is correct with respect to modern periodic law? [RRC Group D 26/09/2022 (Morning)]

Correct Answer: (b) In a neutral atom, the atomic number is equal to the number of electrons or protons.
Solution:

Modern Periodic Law - The elements are arranged according to their increasing atomic number.

32. According to Dobereiner's Triads, which of the following elements could be placed between Calcium and Barium? [RRC Group D 26/09/2022 (Morning)]

(Atomic mass of Ca= 40.1 and atomic mass of Ba= 137.3)

Correct Answer: (d) Strontium (atomic mass = 87.62)
Solution:

Dobereiner's triads - Dobereiner arranged the element in increasing order of atomic masses. He found that the atomic mass of the middle element was approximately equal to the arithmetic mean (average) of the atomic masses of the other two elements of that triad when they are arranged in their increasing order of atomic mass.

33. The element 'x' in the modern periodic table has an electronic configuration 2, 8, 8. The element 'x' is placed in the_________. [RRC Group D 26/09/2022 (Evening)]

Correct Answer: (c) 18th group
Solution:

Element X is Argon. Noble gas- The six naturally occurring noble gasses are Helium(He), Neon(Ne), Argon(Ar), Krypton(Kr), Xenon(Xe), and Radon(Rn). Transition Metals - Group 3 to Group 12. Incandescent lightbulbs are typically filled with inert gases such as argon.

34. Which elements show similar valency as that of silicon? [RRC Group D 26/09/2022 (Evening)]

Correct Answer: (a) C and Ge
Solution:

Carbon and Germanium (Group 14 - Periodic Table): Both have the same number of valence electrons (4). Carbon: Recognized as an element by - Antoine Lavoisier in 1789, Atomic mass - 12. Germanium: Discovered by - Clemens Alexander Winkler in 1886, Atomic mass - 72.

35. The correct increasing order of metallic character is : [RRC Group D 27/09/2022 (Morning)]

Correct Answer: (a) Ge<Ga < Sc < Ca
Solution:

Metallic Character is the tendency of an element to lose electrons and form positive ions or cations. Increases down the group and decreases across a period. The elements of Period 4 are Potassium (K), Calcium (Ca), Scandium (Sc), Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Gallium (Ga), Germanium (Ge), Arsenic (As), Selenium (Se), Bromine (Br) and Krypton (Kr).

36. Which of the following acts as the deciding factor in the determination of the valency of an atom? [RRC Group D 27/09/2022 (Morning)]

Correct Answer: (b) Number of electrons in the outermost shell
Solution:

Valency: The ability to combine atoms of elements with each other is called valency. The electrons present in the outermost shell of the atom are called valence electrons or outer-shell electrons. The outermost shell or the valence shell is the shell having the highest energy.
The electrons present in the valence shell possess the highest energy compared to the electrons present in the inner orbits. This shell is the farthest from the nucleus. As a result, they may be attracted as much or more by the nucleus of another atom as by their nucleus.

37. Arrange the following elements in the order of increasing atomic number. [RRC Group D 27/09/2022 (Afternoon)]

B, Ne, K, O

Correct Answer: (c) B, O, Ne, K
Solution:

B (Boron, 5), O (Oxygen, 8), Ne (Neon,10), K (Potassium, 19). As we move down the group, Atomic radius increases, Ionization energy and Electronegativity (Except for group 11) decrease.
On moving left to right in a period, Atomic size decreases and Ionization energy, Electronegativity and Electron affinity (Except for noble gas) increase.

38. According to Newland's law of octaves, how many elements are present in between Potassium and Copper? [RRC Group D 28/09/2022 (Afternoon)]

Correct Answer: (d) 7
Solution:

According to Newlands' Law of Octaves, there are 56 elements that exist in nature. The repetition in the properties of the eight elements with the properties of the first element is similar to the repetition of the eighth element. The Law of Octaves was true only for Elements up to Calcium.

39. In Dobereiner's Triads, elements were written as: [RRC Group D 28/09/2022 (Evening)]

Correct Answer: (c) down the group with increasing atomic masses
Solution:

Dobereiner's Triad - Dobereiner placed three elements of similar properties together such that the arithmetic mean of the atomic masses of the first and third element in a triad would be approximately equal to the atomic mass of the second element in that triad. Example - Lithium (6.94), Sodium (22.99), Potassium (39.1).

40. Which two elements were put in the same slot by Newland? [RRC Group D 28/09/2022 (Evening)]

Correct Answer: (d) Co and Ni
Solution:

Newlands law of octaves: If the chemical elements are arranged according to increasing atomic weight, Atoms that have similar physical and chemical properties occur after each interval of seven elements.
Limitations: Some elements having dissimilar properties were also placed together, the law was valid up to calcium, the elements discovered later could not be placed in the octave pattern.