# CBSE Important Questions(5 mark questions) for CBSE Class 10 Science PERIODIC CLASSIFICATION OF ELEMENTS

Q1. Would you place the two isotopes of chorine, Cl-35 and Cl-37 in different slots because of their different atomic masses or in the same slot because of their chemical properties are the same? Justify your answer.
Q2. (a) What is Modern Periodic Law?
(b) Atomic masses of nickel and cobalt are respectively 58.7 and 58.9. Which of them should appear first in the Periodic Table?
(c) In which groups of the Periodic Table are the elements germanium and strontium present?
(d) What is meant by the Law of Octaves?
(e) Which has the bigger size:-
(i) out of chlorine and bromine?
(ii) out of sodium and magnesium?
Q4. The elements of a period of the Periodic Table are given below in order, from left to right with one of its element missing.
Li      Be     B    C     O    F    Ne
(i) To which period do these elements belong?
(ii) One element of this period is missing. Which I the missing element and where should it be placed?
(iii) Which one of these elements in this period shows the property of catenation?
(iv) Which one of the above elements belong to the halogen series?
(v) Identify the noble gas.

Q5. An element X which is a yellow solid at room temperature shows catenation and allotropy. X form two oxides which are also formed during the thermal decomposition of ferrous sulphur crystals and are the major air pollutants.
(a) Identify the element X.
(b) Write the electronic configuration of X.
(c) Write the balanced chemical of equation for the thermal decomposition of ferrous sulphate crystals.
(d) What would be the nature (acidic/ basic) of oxides formed?
(e) Locate the position of the element in the Modern Periodic Table.
Q6.  Out of N and F, which atom do you think will be more electronegative and why?
Q7. An element X (atomic no. 11) reacts with an element Y (atomic no. 17) to form a monovalent halide.
(a) Identify the position of X and Y in group and period in the Periodic Table.
(b) State whether these elements are metal or non- metal.
(c) Describe nature of oxide of element X.
(d) Draw electron dot structure of the halide.
Q8. Two elements X an Y have atomic number 11 and 16 respectively.
(i) Write the electronic configuration of both.
(ii) Which type of bond will they form?
(iii) Write the formula of the compound formed by their combination (in terms of X and Y).

Given below are the links of some of the reference books for class 10 Science.

You can use above books for extra knowledge and practicing different questions.

### Practice Question

Question 1 Which among the following is not a base?
A) NaOH
B) $NH_4OH$
C) $C_2H_5OH$
D) KOH
Question 2 What is the minimum resistance which can be made using five resistors each of 1/2 Ohm?
A) 1/10 Ohm
B) 1/25 ohm
C) 10 ohm
D) 2 ohm
Question 3 Which of the following statement is incorrect? ?
A) For every hormone there is a gene
B) For production of every enzyme there is a gene
C) For every molecule of fat there is a gene
D) For every protein there is a gene

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