CBSE Notes, Lectures

CBSE - Chemistry - Periodic Classification of Elements

Periodic Classification of Elements

MCQ

Periodic classification of Elements MCQ 1

14. Which of the following elements would lose an electron easily?
(a) Mg
(b) Na
(c) K
(d) Ca
Ans. (b) Na
Explanation: Na, K and Ca belong to the same group, i.e. Group I. But Na is at the top among them. Hence, sodium would lose an electron more easily compared to others. Mg belongs to groups II and hence would not lose electrons as easily as Na.

15. Which of the following elements does not lose an electron easily?
(a) Na
(b) F
(c) Mg
(d) Al
Ans. (b) F
Explanation: Sodium has 1, Mg has 2 and Al has 3 electrons in outermost orbits. But F has 7 electrons in its outermost orbit. Hence, F does not lose an electron easily.

16. Which of the following are the characteristics of isotopes of an element?
(i) Isotopes of an element have same atomic masses.
(ii) Isotopes of an element have same atomic number.
(iii) Isotopes of an element show same physical properties.
(iv) Isotopes of an element show same chemical properties.
(a) (i), (iii) and (iv)
(b) (ii), (iii) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)
Ans. (d) (ii) and (iv)
Explanation: Isotopes of an element have same atomic number but different atomic masses. They show same chemical properties but different physical properties.

17. Arrange the following elements in the order of their decreasing metallic character
Na, Si, Cl, Mg, Al
(a) Cl > Si >Al > Mg >Na
(b) Na >Mg >Al >Si > Cl
(c) Na > Al > Mg > Cl > Si
(d) Al > Na> Si > Ca> Mg
Ans. (b) Na>Mg>Al>Si>Cl
Explanation: Sodium has 1, Mg has 2 and Al and 3, Si has 4 electrons in outermost orbits. But Cl has 7 electrons in its outermost orbit. Hence, sodium shows the maximum character of metallic element and chlorine shows the character of non-metallic element.
It is important to remember that electropositive elements are metallic in character.

18. Arrange the following elements in the order of their increasing non-metallic character Li, O, C, Be, F
(a) F < O < C < Be < Li
(b) Li < Be < C < O< F
(c) F < O < C < Be < Li
(d) F < O < Be < C < Li
Ans. (b) Li < Be < C < O < F
Explanation: Li is at the extreme left of 2nd period; followed by Be. Fluorine is at extreme right of the second period; just before Neon. Hence, F shows the maximum character of a non-metal. Li and Be are metals.

19. What type of oxide would Eka– aluminium form?
(a) EO3
(b) E3O2
(c) E2O3
(d) EO
Ans. (c) E2O3
Explanation: Eka-aluminium is in the same group as Aluminum, i.e. Group 13. Hence, there are 3 electrons in its outermost orbit. So, it can lost 3 electrons to form a bond. Oxygen has 6 electrons in its outermost orbit which means it can gain 2 electrons to form a bond.

20. Three elements B, Si and Ge are
(a) metals
(b) non-metals
(c) metalloids
(d) metal, non-metal and metalloid respectively
Ans. (c) Metalloids
21. Which of the following elements will form an acidic oxide?
(a) An element with atomic number 7
(b) An element with atomic number 3
(c) An element with atomic number 12
(d) An element with atomic number 19
Ans. (a) An element with atomic number 7
Explanation: Element with atomic number 7 has following electronic configuration: 2,5. This means, it can gain 3 electrons to make a bond and this is an electronegative element. So, this a non-metal. Non-metals make acidic oxide.

22. The element with atomic number 14 is hard and forms acidic oxide and a covalent Halide. To which of the following categories does the element belong?
(a) Metal
(b) Metalloid
(c) Non-metal
(d) Left-hand side element
Ans. (b) Metalloid
23. Which one of the following depicts the correct representation of atomic radius(r) of an atom?

(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Ans. (b) (ii) and (iii)
Explanation: The distance between nucleus and outermost orbit is called atomic radius.In fig (iii), it is quite clear. In fig (ii), only the first orbit contains electron and hence this fig shows correct depiction of atomic radius.

24. Which one of the following does not increase while moving down the group of the
periodic table?
(a) Atomic radius
(b) Metallic character
(c) Valence
(d) Number of shells in an element
Ans. (c) Valence
Explanation: Valence of an element remains the same in a group.

25. On moving from left to right in a period in the periodic table, the size of the atom.
(a) increases
(b) decreases
(c) does not change appreciably
(d) first decreases and then increases
Ans. (b) Decreases
Explanation: Atomic radius decreases when we move from left to right in a period. Hence, size of atom also decreases.

26. Which of the following set of elements is written in order of their increasing metallic character?
(a) Be Mg Ca
(b) Na Li K
(c) Mg Al Si
(d) C O N
Ans. (a) Be Mg Ca
Explanation: These elements are in same group but Be is at the top, while Ca is at
bottom. Metallic character increases as we move down the group.

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