Ch. 8 Periodic Classification Extra Questions

-
Q. Write 3 features of Mendeleev's periodic table.

 A.・Elements are arranged according to their increasing atomic masses.
・There are 6 periods (horizontal rows) and 8 groups (vertical columns).
・Periods 4, 5 and 6 are divided into 2 halves.

 Q. Which physical and chemical properties of the elements were used by Mendeleev in creating his periodic table? List two observations which posed a challenge to Mendeleev's periodic law.

 A. Physical property used by Mendeleev was the atomic masses of elements and the chemical property used by him was the similar formulae of their oxides and hydrides.

 2 challenging observations:

 i) The position of isotopes: Isotopes are the atoms of same elements with different atomic masses and hence would be provided with different spaces in Mendeleev's periodic table.

 ii) The position of hydrogen: Hydrogen resembles both alkali metals as well as halogens but it was placed with halogens in this table.

 Q. How and why does the atomic size vary as you go:
i) from left to right across a period
ii) down a group

 A. i)Atomic size decreases across a period as the number of shells remains the same but the nuclear charge increases due to increase in the number of protons. (Noble gases are an exception as they have bigger atomic size than halogens.)

 ii) Atomic size increases down the group as the number of shells increases and the effective nuclear charge (ENC) decreases.

Q. How will the tendency to gain electrons change as we go from left to right across a period? Why?

A. The tendency to gain electrons i.e. electronegativity increases across a period as the number of electrons increases but the number of shells remains same.

 Q. How does the electronic configuration of atoms change in a period with increase in atomic number?

 A.In a period, as we go from left to right, the number of electrons (and the number of protons) increases as the atomic number increases but the number of shells remains same. Thus valency first increases and then decreases.

 Q. Why was the system of classification into triads not found suitable?

 A. Classification of elements was not found suitable because of the variations in the atomic masses observed and calculated. Moreover, only a few elements could be classified into triads.

 Q. Elements have been arranged in the following sequence on the basis of their increasing atomic masses:
F, Na, Mg, Al, Si, P, S, Cl, Ar, K
i) Pick 2 sets of elements which have similar properties.
ii) The given sequence represents which law of classification of elements?

 A. i) F and Cl, Na and Ar.

 ii) The sequence represents Newland's law of octaves.

Popular posts from this blog

Class 9 History Ch.1 The French Revolution Extra Questions

-
Q. Who were the active citizens? A. Active citizens were the men who were above 25 years of age and paid taxes equal to at 3 days of a labourer's wage. These citizens had the right to vote. Q. Who were the passive citizens? A.  Passive citizens were the men and all women who were not entitled to vote. Q.  What were the taxes paid by the 3rd estate members of French society. A.  The taxes paid by the 3rd estate members were- i) Tithes - It was a tax levied by the church comprising of one-tenth of the agricultural produce. ii) Taille - It was a tax to be paid directly to the state. iii) Gobelle - It was an indirect tax on essential commodities like salt and tobacco consumption. Q. What was the Estates General? A.  The Estates General was a political body to which the 3 estates sent their representatives. This was the body which had the power to pass or reject the proposals for new taxes made by the monarch. Q. What was the import...
Read more

P.6 Oh, I Wish I'd Looked After Me Teeth (Pam Ayres)

-
Q. RTC "I wish I'd been that much more willin' When I had more tooth there than fillin' To pass up gobstoppers. From respect to me choppers, And to buy something else with me shillin'." a) ' I wish I'd been that much more willin' ' What does this line tell us about the poetess. a)  This line tells that the poetess now regrets not taking appropriate care of her teeth. b) What the poetess should not have bought with the shillings to avoid cavities? b) The poetess should not have bought candies, gobstoppers and other sweet food which she relished but was harmful to her teeth. c) What is the tone of the poetess in the poem? c)  The tone of the poetess is that of regret and repentance. Q. Imagine you are the poet. The day you visit the dentist for the first time, you write a letter to your best friend. Express the dilemma of guilt that you experience. A. 21-B, Baker's Street London 23 July 1989 Dear Robert         ...
Read more

P 6: Snake (by D.H. Lawrence)

-
Q. The poet has a dual attitude towards the snake. Why does he experience conflicting emotions on seeing the snake? A. When the poet first sees the snake, he thinks of the snake as a magnificent, quasi-harmless creature. He gives it as much respect as he gives to any other human. But soon the 'voice of education', i.e. the man-centric education challenges the poet to kill the snake lest he lacks the courage to do so. Q. Why did the snake flicker its tongue? And what does the poet compare it to? A. The snake uses its tongue as a sense organ. It flickers its tongue to check whether its surroundings are safe or not. The poet compares this flickering to lightning. The lightning on a dark night is easily comparable to the snake's tongue and its realm of the underworld. Q. RTC "And immediately I regretted it  I thought how paltry, how vulgar, what mean act! I despised myself and the voices of my accursed human education  And I thought of the albatross...
Read more