Answer:
1. Answer : (d) diagonal relationship
Explanation: The chemistry of lithium is very similar to that of magnesium even though they are placed in different groups because of diagonal relationship.
2. Answer : (a) B < Be < C < O < N
Explanation: The amount of energy required to remove an electron from the outermost orbit of a gaseous atom is known as ionisation potential. Elements having half-filled or completely filled' orbitals are more stable than partially filled orbitals. In a period from left to right ionisation potential decreases as the atomic number increases. The given elements (Be, B, C, N, O) are present in II period as Be < B< C < N < O. But in case of Be and B, Be has higher ionisation potential due to stable configuration So, the correct order of increasing ionisation potential will be B < Be < C < O <N
3. Answer : (c) s and p – Block
Explanation: The representative elements are all the elements in groups one, two, thirteen, fourteen, fifteen, sixteen, seventeen and eighteen of the periodic table. These include metals, non metals and semi metals (metalloid).
4. Answer : (b) Metallic Character
Explanation: Along a period the electropositive character decreases, therefore the ionization energy, electron affinity and valency increases while metallic character decreases.
5. Answer : (c) O
Explanation: According to Pauling's electronegativity scale, oxygen (O) has an electronegativity value of approximately 3.5, which is next to fluorine (F) with electronegativity value of approximately 4.
6. Answer : (a) SnO2
Explanation: A species is amphoteric if it is soluble in acid (behaves as a base) as well as in base (behaves as an acid).
SnO2 + 4HCl → SnCl4 + 2H2O
SnO2 + NaOH→ Na2SnO3 + H2O
7. Answer : (c) Principal Quantum Number
Explanation: In the modern periodic table, each period begins with the filling of a new shell. Therefore, the period indicates the value of principal quantum number.
8. Answer : (c) Group 16 and period 5
Explanation: ns2np4 → VI A group
16th group, n = 5 (5th period)
9. Answer : (a) 81.25
Explanation: According to Dobereneir's triads, the atomic mass of Br will be average of the atomic masses of CI & I.
\(=\frac{35.5+127}{2}\)
= 81.25
10. Answer : (a) arsenic
Explanation: According to Dobereiner, the atomic mass of the middle element was nearly equal to the arithmetic mean of the other two. Therefore, the atomic mass of the third element is \(=\frac{31+121.75}{2}\) = 76.37 which is nearly equal to the atomic mass of arsenic.
11. Answer :(a) chemical properties
Explanation: Johann Dobereiner in early 1800's was the first to consider the idea of trends among properties of elements. By 1829 he noted a similarity among the physical and chemical properties of several groups of three elements (triads).
12. Answer : (a) calcium
Explanation: He could classify only elements upto calcium, out of 56 known elements at his time. In order to fit in his table, He kept 2 elements in one slot which may differ in property. Some similar properties elements were separated far apart.
13. Answer : (a) 118
Explanation: At present, 118 elements are known to us. All these have different properties. Out of these 118, only 94 are naturally occurring.
14. Answer : (a) Moseley
Explanation: It was Henry Moseley who suggested a better arrangement than Mendeleev. He arranged the elements according to their Atomic Number rather than their Atomic mass.
15. Answer : (a) 32
Explanation: The sixth period contains 32 elements, tied for the most with period 7, beginning with caesium and ending with radon. Lead is currently the last stable element; all subsequent elements are radioactive.
16. Answer : (a) Mosley’s work on X-ray spectra
Explanation: Henry Moseley observed regularities in the characteristic X-ray spectra of the elements by plotting square root of frequency of x-rays against atomic number which gave a straight line.
17. Answer : (a) K+
Explanation: K+ ion will form most water soluble hydroxide because it is the most reactive of these metals and thus forms strong alkali KOH which will undergo complete dissociation in water, thus making it highly soluble.
18. Answer : (b) Fr
Explanation: Francium belongs to alkaline earth metals having one electron in outermost shell. After losing an electron it will acquire noble gas configuration , so it has the maximum tendency to lose an electron.
19. Answer : (a) Ionization energy
Explanation: Gradual addition of electronic shells in the noble gases causes a decrease in their ionisation energy. On moving down the group, number of shells and atomic radius increases. Shielding of outer electrons by inner electrons increases. This decreases the force of attraction between outermost electrons and nucleus. Effective nuclear charge and ionisation enthalpy decreases.
20. Answer : (c) Nitrogen
Explanation: Nitrogen has the highest first ionization energy, though it should have less than that of oxygen while going across a period. The electronic configuration of nitrogen is 1s2,2s2,2px1,2py1,2pz1.Nitrogen has three electrons in 2p subshell which are singly filled. So, nitrogen is in a stable state and does not want to lose electrons. Hence, it has the highest first ionization energy.
21. Answer : (d) Atomic size and nuclear charge both
Explanation: Electron affinity is the amount of energy released when an electron is added to a neutral atom to form a negative ion. EA decreases on moving down the group as the atomic size increases and net nuclear charge increase is offset by extra screening electrons as the additional electron enters an orbital away from the nucleus. So, it is less attracted to nucleus and would release less energy when added.
22. Answer : (a) At anode
Explanation: Hydrogen gas is liberated at the anode as sodium hydride exists as sodium cation and hydride anion. Therefore hydrogen gas is liberated at anode by lose of electrons at anode (oxidation).
23. Answer : (a) Li
Explanation: Lithium is the element that is atomic number 3 on the periodic table. That means each atom contains 3 protons. Lithium is a soft, silvery, light alkali metal denoted with the symbol Li.
24. Answer : (d) Pd
Explanation: The coinage metal comprise, at a minimum, those metallic chemical elements which have historically been used as components in alloys used to mint coins.
25. Answer : (a) Ga and Ge
Explanation: Mendeleev name unnamed elements as EKA- Boron EKA- Aluminium and EKA Silicon which were later replaced as Scandium, Gallium, and germanium respectively. .Eka aluminum is the element Gallium. Eka silicon – It is the element Germanium.
Click here to practice MCQ Questions for Classification of Elements and Periodicity in Properties class 11