"AKC SCIENCE CLASSES"
CLASS 10 TH (CBSE AND MP BOARD)
CHAPTER 05
PERIODIC CLASSIFICATION OF ELEMENTS
EXERCISE QUESTIONS AND ANSWERS
Q.01:- Which of the following statements is not a 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 valence electrons increases.
(c) The atoms lose their electrons more easily.
(d) The oxides become more acidic.
Ans:- (c) The atoms lose their electrons easily when going to right is not correct.
Q.02:- Element X forms a chloride with the formula XCl2, 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.
Q.03:- Which element has
(a) two shells, both of which are completely filled with electrons?
(b) the electronic configuration 2, 8, 2?
(c) a total of three shells, with four electrons in its valance shell?
(d) a total of two shells, with three electrons in its valance shell?
(e) twice as many electrons in its second shell as in its first shell?
Ans:- (a) Ne (2,8)
(b) Mg (2,8,2)
(c) Si (2,8,4)
(d) B (2,3)
(e) C (2,4)
Q.04:- (a) What property do all elements in the same column of the Periodic Table as boron have in column?
(b) What property do all elements in the same column of the Periodic table as fluorine have in common?
Ans:- (a) Elements in the same column or group as boron have valence of three and are metalloids or semi-metals.
(b) Elements in the same column or group as fluorine from acidic oxides and have seven electrons in their outermost shells.
Q.05:- An atom has electronic configuration 2, 8, 7.
(a) What is the atomic number of this element?
(b) To which of the following elements would it be chemically similar? (Atomic numbers are given in parentheses.)
N (7) F (9) P (15) Ar (18)
Ans:- (a) 17 (b) F (9).
Q.06:- The position of three elements A, B and C in the Periodic Table are shown below :-
Group 16 Group 17
---- ----
---- A
---- ----
B C
(a) State whether A is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller in size than B?
(d) Which type of ion, cation or anion, will be formed by element A?
Ans:- (a) A is a non-metal.
(b) C is less reactive than A.
(c) C is smaller in size than B.
(d) A will form anion.
Q.07:- Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the Periodic Table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why?
Ans:- Electronic configuration of nitrogen :- 2, 5
Electronic configuration of phosphorus :- 2, 8, 5
Nitrogen will be more electronegative because outermost shell is nearer to nucleus and thus nucleus will attract electrons more strongly.
Q.08:- How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?
Ans:- The position of an atom/element in the periodic table is related to the number of electrons in the outermost shell. In a given column or group, all elements have the same number of electrons in their outermost shells. For example, in group 11, all elements have two electrons in their outermost shell. In group 15, all elements have 5 electrons in their outermost shells.
Q.09:- In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21, and 38. Which of these have physical or chemical properties resembling calcium?
Ans:- The electronic configuration of elements :-
Atomic Number 12 : 2, 8, 2
Atomic Number 19 : 2, 8, 8, 1
Atomic Number 20 (Ca) : 2, 8, 8, 2
Atomic Number 21 : 2, 8, 8, 3
Atomic Number 38 : 2, 8, 8, 8, 8, 4
The elements having atomic numbers 12 and 38 have their physical and chemical properties similar to those of calcium because they have same number of valence electrons.
Q.10:- Compare and contrast the arrangement of elements in Mendeleev's Periodic Table and the Modern Periodic Table.
Ans:-
| SL No. | Mendeleev's Periodic Table | Modern Periodic Table |
|---|---|---|
| 1 | Elements are arranged in the order of increasing atomic masses. | Elements are arrange in the order of increasing atomic numbers. |
| 2 | There are a total of 7 groups (columns) and 6 periods (rows) | There are a total of 18 groups (columns) and 7 periods (rows) |
| 3 | Elements having similar properties were placed directly under one another. | Elements having the same valence shell are present in the same period while elements having the same number of valence electrons are present in the same group. |
| 4 | The position of hydrogen could not be explained. | Hydrogen is placed above alkali metals. |
| 5 | No distinguishing positions for metals and non-metals. | Metals are present at the left hand side of the periodic table whereas non-metals are present at the right hand side. |
