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

Total Questions: 50

1. The electronic configuration of an element belonging to period 2 and showing strong catenation property is : [RRB Group D 18/09/2018 (Afternoon)]

Correct Answer: (b) 2, 4
Solution:

Catenation : The capability of atoms forming a long chain by bonding with each other. Carbon (C, atomic number - 6) shows catenation property the most but Silicon, sulphur and boron also show it to some extent.
2, 8, 2 : Magnesium (Mg) - 3rd period (row), Group 2, atomic number 12. 2, 6 : Oxygen (O) - 2nd period, Group 16, atomic number 8. 2, 8, 4 : Silicon (Si) - 3rd period, Group 14, atomic number 14.

2. If the electronic configuration of an element is 2, 8, 2 to which period of the Modern Periodic Table does it belong ? [RRB Group D 18/09/2018 (Afternoon)]

Correct Answer: (d) 3
Solution:

Magnesium with atomic number 12, has the electronic configuration 2, 8, 2. The third period contains eight elements : sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine and argon. Electronic configuration - The arrangement of electrons in orbits around the atomic nucleus.

3. The atomic size _______ while moving from sodium to chlorine. [RRB Group D 18/09/2018 (Evening)]

Correct Answer: (b) decreases
Solution:

In a group, the size of an atom increases as one proceeds from top to bottom. In a period, the size of an atom decreases from left to right. The atomic radius of an element is a measure of the size of its atom, usually, the distance from the center of the nucleus to the outermost isolated electron.

4. Eka - Aluminium was named as _____ metal in the modern periodic table. [RRB Group D 18/09/2018 (Evening)]

Correct Answer: (b) Gallium
Solution:

Mendeleev also coined the term ‘Eka-boron’ to describe an undiscovered element that is now known as Scandium. He termed Germanium as ‘Eka-silicon’ which meant ‘beyond silicon’.

5. Which of the following elements has the higher ionization energy ? [RRB Group D 18/09/2018 (Evening)]

Correct Answer: (d) He
Solution:

Helium (He) has the highest ionization energy, while caesium (Cs) and francium (Fr) have one of the lowest. The ionization energy decreases from top to bottom in groups, and increases from left to right across a period.

6. Elements in the third period have shells_________. [RRB Group D 18/09/2018 (Evening)]

Correct Answer: (c) K, L and M
Solution:

The third period of the periodic table, includes elements from sodium (Na) to argon (Ar). On moving down a group in the periodic table, the number of shells in the atoms of the elements increases.

7. An atom which has a complete number of electrons in its outer orbit has __________ valency. [RRB Group D 18/09/2018 (Evening)]

Correct Answer: (d) zero
Solution:

When an atom has a complete octet (i.e., a full outer shell with eight electrons), its valency is zero because it does not need to gain, lose, or share any more electrons to achieve stability. Valency refers to the number of electrons an atom can gain, lose, or share to achieve a stable electron configuration.

8. Which of the following elements is more electronegative? [RRB Group D 18/09/2018 (Evening)]

Correct Answer: (b) Cl
Solution:

Electronegativity is a qualitative measure of the ability of an atom in a chemical compound to attract shared electrons to itself. In the periodic table, electronegativity generally increases across a period from left to right (from lithium to fluorine) and decreases from top to bottom in a group (from fluorine to astatine).

9. Which of the following elements could not find a definite place in Mendeleev's periodic table? [RRB Group D 19/09/2018 (Morning)]

Correct Answer: (a) Hydrogen
Solution:

Hydrogen has unique characteristics. It is placed in the first group of the periodic table due to its electronic configuration, but it also exhibits properties similar to those of alkali metals and halogens. Additionally, its atomic mass is lower than any other element in Group 1.

10. Newlands theory of octaves was applicable only till ________. [RRB Group D 19/09/2018 (Morning)]

Correct Answer: (a) Calcium
Solution:

In 1866, John Newlands, an English scientist, arranged the then known elements in the order of increasing atomic masses. He started with the element having the lowest atomic mass (hydrogen) and ended at thorium which was the 56th element. It was found that the Law of Octaves was applicable only up to calcium, as after calcium every eighth element did not possess properties similar to that of the first.