CBSE Class 10 Science Chapter-5 Periodic Classification of Elements Important Questions – Free PDF Download
Free PDF download of Important Questions with Answers for CBSE Class 10 Science Chapter 5 – Periodic Classification of Elements prepared by expert Science teachers from latest edition of CBSE(NCERT) books only by CoolGyan to score more marks in CBSE board examination.
CBSE Class 10 Science Periodic Classification of Elements Chapter-5 Important Questions
CBSE Class 10 science Important Questions Chapter 5 – Periodic Classification of Elements
1 Mark Questions
1. Arrange the following in descending atomic size Na, Mg, K
Ans. K, Na, Mg
2. Give the name and electronic configuration of second alkali metal?
Ans. Sodium (Na) (2, 8, 1)
3. What is the similarity in the electronic configuration of Mg, Ca and Sr?
Ans. All the elements have two electrons in their valence shell.
4. Which is bigger in size Na, Na+
Ans. Na
5. Name three elements which behave as metalloids?
Ans. Arsenic (As), Antimony (Sb), Germanium (Ge)
6. Which of the following has maximum atomic size?
(a) K
(b) Ca
(c) Al
(d) P
Ans. (a) K
7. The law of octaves was proposed by
(a) Newland
(b) Doberiener
(c) Lother Meyer
(d) Mendleeve
Ans. (a) Newland
8. The number of periods in the long form of the periodic table is
(a) 6
(b) 7
(c) 10
(d) 18
Ans. (b) 7
9. Which of the following elements has maximum metallic character?
(a) Li
(b) N
(c) Na
(d) P
Ans. (c) Na
10. Which of the following is the most reactive halogen?
(a) F
(b) Cl
(c) Br
(d) I
Ans. (a) F
11. Besides gallium, which other elements have since been discovered that were left by Mendeleev in his Periodic Table? (any two)
Ans. 
12. Which of the following statements is not correct statement about the trends when going from left to right across the periods of Periodic Table?
(a) The elements become less metallic in nature.
(b) The number of valance electrons increases.
(c) The atoms lose their electrons more easily.
(d) The oxides becomes more acidic.
Ans. (c) The atoms lose their electrons more easily.
13. Element X forms a chloride with the formula 
which is a solid with a high melting point. X would most likely be in the same group of the Periodic Table as
(a) Na
(b) Mg
(c) Al
(d) Si
Ans. (b) Mg
14. X, Y and Z are the elements of a dobereiners triad. If the atomic mass of x is 7 and that of z is 39, what should be the atomic mass of y?
Ans. (7+39) = 46/2 y=23.
15. A and B are the two elements having similar properties which obey Newlands law of octaves. How many elements are there in between A and B?
Ans. Six elements.
