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

Total Questions: 50

31. The atomic number of actinium is: [RRB Group D 09/10/2018 (Afternoon)]

Correct Answer: (a) 89
Solution:

Actinium (Ac): Its estimated shear modulus is similar to that of lead. Some elements and its atomic numbers: Thorium (Th) - 90, Radium (Ra) - 88, Protactinium (Pa) - 91, Lanthanum (La) - 57, Uranium (U) - 92.

32. _________ is an unsaturated hydrocarbon. [RRB Group D 10/10/2018 (Morning)]

Correct Answer: (c) Benzene
Solution:

It is an organic chemical compound with the molecular formula C6H6 . It appears as a clear colorless liquid with a petroleum-like odor. Flash point less than 0 °F. Less dense than water and slightly soluble in water. Hence floats on water.

33. According to Newlands' octet rule, iron, which resembles ________ and _____ in properties, is placed far away from these elements. [RRB Group D 10/10/2018 (Evening)]

Correct Answer: (a) Co and Ni
Solution:

Newlands’s law of octaves - In 1866, John Newlands, arranged the elements in order of increasing atomic masses, starting with hydrogen and ending at thorium. He observed that every eighth element had properties similar to the first which led to the concept of "octaves".

34. Identify the element having electronic configuration 2, 6. [RRB Group D 10/10/2018 (Evening)]

Correct Answer: (b) Oxygen
Solution:

It is a non metal which is most abundant element in the Earth's crust and atmosphere. Ozone (O₃) is a triatomic allotrope of oxygen. Nitrogen (N) - Atomic number 7. Bromine (Br) - Atomic number 35. It is a reddish-brown liquid at room temperature.

35. In Modern Periodic Table, there is an anomaly when it comes to the position of______because it can be placed either in group 1 or group 17 in the first period. [RRB Group D 11/10/2018 (Morning)]

Correct Answer: (b) H
Solution:

H (Hydrogen) : It combines with halogens so it can be placed in group 1 of the alkali metals and It also exists as a diatomic molecule and forms ionic compounds with metals so it can be placed in the halogen group (17) also.

36. In which of the following classifications are the elements arranged in the order of their increasing atomic number? [RRB Group D 11/10/2018 (Morning)]

Correct Answer: (a) The Modern Periodic Table
Solution:

Mendeleev’s Periodic Table - The elements are arranged in the order of their atomic masses. Newland’s Law of Octaves - The elements are arranged in the order of their increasing atomic masses and every 8th element has similar properties.

37. ______ is least reactive element belonging to group 17. [RRB Group D 11/10/2018 (Morning)]

Correct Answer: (b) Iodine
Solution:

Properties - Non-metallic, dark-gray/purple-black, Lustrous, Solid. Other non metallic elements of group 17 - Fluorine (F), Chlorine (Cl), Bromine (Br), Astatine (At).
Reactivity of an element - determined by a number of factors, including its atomic radius, electronegativity, and ionization energy.
Most Reactive element of group 17 - Fluorine. Atomic radius - decreases ( move from left to right in a period) and increases (go down a group).

38. The atomic mass of Calcium is: [RRB Group D 11/10/2018 (Morning)]

Correct Answer: (b) 40
Solution:

Atomic mass - Discovered by - Dalton. Theory - Atomic Theory of dalton. 1 Atomic mass = Mass of 1/12 the mass of a carbon - 12 atom. Other elements with their Atomic masses - Hydrogen (H₁) - 1 µ, Carbon (C₆ ) - 12 µ, Nitrogen (N₇) - 14 µ, Oxygen (O₈ ) - 16 µ, Magnesium (Mg₁₂) - 24 µ, Sodium (Na₁₁) - 23 µ.

39. Select the item which does not belong to the following group - [RRB Group D 11/10/2018 (Afternoon)]

Correct Answer: (a) Zinc
Solution:

Zinc (Zn) is a metal located in Group 12 (IIB) of the periodic table. It is a lustrous, ductile, and malleable metal that is a good conductor of electricity and heat. It is also a relatively reactive metal and can react with acids and bases to form salts. Neon, Helium, and Argon are all noble gases, belonging to Group 18 (VIII A) of the periodic table.

40. In the modern periodic table, the ________ period consists of only gasses. [RRB Group D 11/10/2018 (Afternoon)]

Correct Answer: (b) 1
Solution:

The 1st period is the shortest period containing only 2 elements i.e. Hydrogen (H) and Helium (He). In this period, only the ‘1s’ orbital filled. There are 18 groups and 7 periods in the modern periodic table which consists of 118 elements.