Class 11 Chemistry - Chapter Classification of Elements and Periodicity in Properties NCERT Solutions | Which important property did Mendeleev u
Which important property did Mendeleev use to classify the elements in his periodic table and did he stick to that?
A Russian chemist, Dmitri Mendeleev was the first to develop a periodic table and he gave a law called Mendeleev periodic law which states that the physical and chemical properties of the elements are a periodic function of their atomic masses. On the basis of this law he developed a Mendeleev periodic table, where he arranged the elements in his periodic table ordered by atomic weight or mass. He arranged the elements in periods and groups in order of their increasing atomic weight. He placed the elements with similar properties in the same group.
However, he did not stick to this arrangement for long. He found out that if the elements were arranged strictly in order of their increasing atomic weights, then some elements did not fit within this scheme of classification.
Therefore, he ignored the order of atomic weights in some cases. For example, the atomic weight of iodine is lower than that of tellurium. Still Mendeleev placed tellurium (in Group VI) before iodine (in Group VII) simply because iodine’s properties are so similar to fluorine, chlorine, and bromine.
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Write the general outer electronic configuration of s-, p-, d- and f- block elements.
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Considering the elements B, Al, Mg, and K, the correct order of their metallic character is:
(a) B > Al > Mg > K
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(c) Mg > Al > K > B
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(ii) Ar
(iii) Mg2+
(iv) Rb+
- Q:-
Considering the elements B, C, N, F, and Si, the correct order of their non-metallic character is:
(a) B > C > Si > N > F
b) Si > C > B > N > F
(c) F > N > C > B > Si
d) F > N > C > Si > B - Q:-
Assign the position of the element having outer electronic configuration
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- Q:-
How does atomic radius vary in a period and in a group? How do you explain the variation?
- Q:-
Use the periodic table to answer the following questions.
(a) Identify an element with five electrons in the outer subshell.
(b) Identify an element that would tend to lose two electrons.
(c) Identify an element that would tend to gain two electrons.
(d) Identify the group having metal, non-metal, liquid as well as gas at the room temperature. - Q:-
Considering the elements F, Cl, O and N, the correct order of their chemical reactivity in terms of oxidizing property is:
(a) F > Cl > O > N
(b) F > O > Cl > N
(c) Cl > F > O > N
(d) O > F > N > Cl - Q:-
On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.
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- Q:-
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Assign oxidation number to the underlined elements in each of the following species:
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(b) NaHSO4
(c) H4P2O7
(d) K2MnO4
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(i) used to determine heat changes
(ii) whose value is independent of path
(iii) used to determine pressure volume work
(iv) whose value depends on temperature only. - Q:-
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a) What is the initial effect of the change on vapour pressure?
b) How do rates of evaporation and condensation change initially?
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Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.
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A sample of drinking water was found to be severely contaminated with chloroform, CHCl3, supposed to be carcinogenic in nature. The level of contamination was 15 ppm (by mass).
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Nice but long
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