Q: The number of protons, neutrons and electrons in 71175Lu, respectively, are:

71175Lu No. of Protons = 71 = No. of ElectronsNo. of Neutrons = Mass no. – No. of Protons = 175 – 71 = 104

Q: The rate constant for a first order reaction is 4.606—10−3s−1. The time required to reduce 2.0 g of the reactant to 0.2 g is :

k=t2.303logAA0 (First order rate equation)4.606×10−3 =t2.303log0.22 t=4.606×10−32.303×log10 =2103=500 sec

Q: In which of the following options the order of arrangement does not agree with the variation of property indicated against it?

N is having ns2np3 (Half filled configuration). Hence has high IP than O which is having ns2np4 electronic configuration.

Q: Which of the following orders of ionic radii is correctly represented?

In exothermic reactions on increasing temperature value of Kp decreases.So, Kp>Kp′

Q: 6.02×1020 molecules of urea are present in 100 mL of its solution. The concentration of solution is:

M=V(ml)mole×1000=1000.001×1000=0.01M

Question 1

Identify the incorrect match. Name IUPAC Official Name(a) Unnilunium (i) Mendelevium(b) Ununtrium (ii) Lawrencium(c) Unnilhexium (iii) Seaborgium(d) Unununium (iv) Darmstadtium

Accepted Answer

UnununiumAtomic number = 111IUPAC official name : Roentgenium

Question 2

The number of protons, neutrons and electrons in 71175​Lu, respectively, are:

Accepted Answer

71175​Lu No. of Protons		= 71 = No. of ElectronsNo. of Neutrons 	= Mass no. – No. of Protons							= 175 – 71							= 104

Question 3

The rate constant for a first order reaction is 4.606—10−3s−1. The time required to reduce 2.0 g of the reactant to 0.2 g is :

Accepted Answer

k=t2.303​logAA0​​  (First order rate equation)4.606×10−3 =t2.303​log0.22​ t=4.606×10−32.303​×log10 =2103​=500 sec

Question 4

For the second period elements the correct increasing order of first ionisation enthalpy is:

Accepted Answer

‘Be’ and ‘N’ have comparatively more stable valence sub-shell than ‘B’ and ‘O’.∴ Correct order of first ionisation enthalpy is: Li < B < Be < C < O < N < F < Ne

Question 5

In which of the following options the order of arrangement does not agree with the variation of property indicated against it?

Accepted Answer

N is having ns2np3 (Half filled configuration). Hence has high IP than O which is having ns2np4 electronic configuration.

Question 6

Which of the following orders of ionic radii is correctly represented?

Accepted Answer

In exothermic reactions on increasing temperature value of Kp​  decreases.So, Kp​>Kp​′

Question 7

6.02×1020  molecules of urea are present in 100 mL  of its solution. The concentration of solution is:

Accepted Answer

M=V(ml)​mole​×1000=1000.001​×1000=0.01M

Question 8

Which is the correct order of increasing energy of the listed orbitals in the atom of titanium? (At. No. Z = 22)

Accepted Answer

Ti(22) = 1s22s22p63s23p64s23d2 Order of energy is 3s 3p 4s 3d

Question 9

What is the basis theme of organisation in the periodic table?

Accepted Answer

The periodic table is organized to simplify and systematize the study of numerous properties of all the elements and their compounds. Similar elements are placed together and dissimilar elements are separated from one another. The study is simple to remember as the properties of elements are studied in the form of groups or families having similar properties rather than studying these elements individually.The long form of the periodic table is based on the fact that the physical and chemical properties of the elements are the periodic functions of their atomic numbers (Modern periodic law). The elements are arranged in the increasing order of their atomic numbers.

Question 10

Which important property did Mendeleev use to classify the element in his periodic table and did he stick to that?

Accepted Answer

The important property that Mendeleev used for the classification of elements was atomic weight. He arranged all known elements in the form of periodic table. Some of the elements did not fit very well if the order of atomic weight was strictly followed. For these elements, he ignored the order of atomic weight (as atomic weight measurements can be incorrect) and placed the elements with similar properties together. Thus, iodine having lower atomic weight than tellurium (of group VI) was placed in group VII along with fluorine, chlorine and bromine due to similar properties and left some gaps for undiscovered elements. By considering the properties the adjacent elements, he predicted the properties of undiscovered elements. Later on, these elements were discovered and their properties were similar to those predicted by Mendeleev. Thus, Mendeleev left gaps for gallium and germanium. He named these elements as eka-aluminium and eka-silicon. When these elements were discovered, their properties were similar to those predicted by Mendeleev.

Question 11

What is the basic difference between the Mendeleev's Periodic Law and the Modern Periodic Law?

Accepted Answer

As per Mendeleev's Periodic Law, the physical and chemical properties of the elements are a periodic function of their atomic weight.Modern Periodic Law the physical and chemical properties of the elements are a periodic function of their atomic number.

Question 12

On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.

Accepted Answer

In the sixth period (n = 6) of the periodic table, 6s, 4f, 5d and 6p orbitals are filled in the increasing order of the energy. Total 16 orbitals are available each of which contains a maximum 2 electrons. Thus, the sixth period can accommodate maximum 32 elements.

Question 13

In terms of period and group where would you locate the element with Z = 114?

Accepted Answer

The element with Z = 114 will have the electronic configuration [Rn]5f146d107s27p2.Thus, the element belongs to the seventh period. The electron enters p orbital. Hence, it belongs to p block. The group number is  10+4=14.The element is FleroviumHence, the element belongs to the seventh period and 14th group.

Question 14

Write the atomic number of the element present in the third period and seventeenth group of the periodic table:

Accepted Answer

The valence shell electronic configuration is  3s23p5. The atomic number of element is 17. It is chlorine.

Question 15

Which element do you think would have been named by (i) Lawrence Berkeley Laboratory and (ii) Seaborg's group?

Accepted Answer

(i) Lawrencium (Z=103).(ii) Seaborgium (Z=106)

Question 16

Why do elements in the same group have similar physical and chemical properties?

Accepted Answer

In the same group, the elements have similar valence shell electronic configuration. Hence, they have similar physical and chemical properties.

Question 17

What does atomic radius and ionic radius really mean to you?

Accepted Answer

Atomic radius is defined as a distance from the center of the nucleus to the outermost shell containing the electrons.Ionic radius is a measure of an atoms ion in a crystal lattice and which is a half distance between two ions that are barely touching each other.

Question 18

How do atomic radius vary in a period and in a group? How do you explain the variation?

Accepted Answer

In a period, from left to right, with increase in the atomic number, the atomic radius decreases due to increase in the nuclear charge which increases the attraction of the nucleus for the valence electrons. In a group, on moving from top to bottom, the ionic radius increases as a new energy level is added at each succeeding element but the number of valence electrons remains same.

Question 19

What do you understand by isoelectronic species? Name a species that will be isoelectronic with each of the following atoms or ions.(i) F− (ii) Ar (iii) Mg2+ (iii) Rb+

Accepted Answer

Isoelectronic species contain same number of electrons. (i) Both  F− and O2− contain 10 electrons each. Hence, they are isolectronic.(ii) Both  Ar and Cl− contains 18 electrons each. Hence, they are isoelectronic.(iii) Both Mg2+ and Na+ contain 10 electrons each. Hence, they are isoelectronic.(iv) Both Rb+ and  Kr contain 36 electrons. Hence, they are isoelectronic.

Question 20

Consider the following species :N3− , O2− ,F−, Na+ , Mg2+and Al3+(a) What is common in them?(b) Arrange them in the order of increasing ionic radii.

Accepted Answer

(a) All the given species contain same number of electrons (10). Hence, they are isoelectronic species. With increase in the nuclear charge, the ionic size decreases.(b) The increasing order of ionic radii is  Al3+<Mg2+<Na+<F−<O2−<N3−.

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