CBSE Class 10 Science 2020 · Paper 31/C/1 · Question 3
Answer question numbers 3(a) – 3(d) on the basis of your understanding of the following paragraph and the related studied concepts :
Matter around us is found in the form of elements, compounds and mixtures. The elements contain atoms of only one type. Around the year 1800, only 30 elements showing different properties were known. Scientists of that age discovered a pattern in their properties and based on that pattern, several attempts were made to classify elements. The earliest attempt was to classify the elements as metals and non-metals. The latest is the ‘Modern Periodic Table’. This table consists of 7 periods and 18 groups. Each element of a group in the periodic table has the identical outer shell electronic configuration. In other words, the groups in the periodic table signify an identical outer shell electronic configuration. As we go down the group in the periodic table, the number of shells increases.
- (a)Write the need to classify elements.[1]
- (b)How many groups are there in the ‘Modern Periodic Table’ ?[1]
- (c)Which one of the following statements is not correct about the ‘Modern Periodic Table’ ? (A) It is based on atomic masses. (B) The position of isotopes is not disputed. (C) The position of isotopes is easily assigned. (D) It separates metals from non-metals.[1]
- (d)The cause of periodicity of properties of elements is (A) Increasing atomic radius (B) Increasing atomic mass (C) Increasing nuclear charge (D) The recurrence of similar outer electronic configuration[1]
Answer
Classification makes study systematic; there are 18 groups; statement (A) is incorrect; periodicity is due to recurring similar outer electronic configurations.
(a) As more elements were discovered, it became difficult to study each element and its compounds separately. Classification groups elements with similar properties together, which makes their study systematic and easy and helps to predict the properties of elements.
(b) groups (and periods).
(c) (A) It is based on atomic masses. The Modern Periodic Table is based on atomic numbers.
(d) (D) The recurrence of similar outer electronic configuration.
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