CBSE Class 9 Science Periodic Classification of Elements MCQs

Question. The third member of the Dobereiner triad consisting of lithium and sodium is :
(a) Potassium
(b) Hydrogen
(c) Boron
(d) Barium
Answer : A

Question. If the two members of a Dobereiner triad are chlorine and iodine, the third member of this triad is :
(a) Fluorine
(b) Bromine
(c) Sodium
(d) Calcium
Answer : B

Question. If the two members of a Dobereiner triad are sulphur and selenium, the third member of this triad is :
(a) Calcium
(b) Barium
(c) Strontium
(d) Tellurium
Answer : D

Question. If the two members of a Dobereiner triad are phosphorus and antimony, the third member of this triad is :
(a) Arsenic
(b) Sulphur
(c) Iodine
(d) Calcium
Answer : A

Question. Who gave the 'law of octaves'?
(a) Dobereiner
(b) Lothar meyer
(c) Mendeleef
(d) Newlands
Answer :  D

Question. Upto which element, the Law of Octaves was found to be applicable
(a) Oxygen
(b) Calcium
(c) Cobalt
(d) Potassium
Answer : B

Question. Increasing order of electro negativity is
(a) Bi < P < S < Cl
(b) P < Bi < S < Cl
(c) S < Bi < P < Cl
(d) Cl < S < Bi < P
Answer : A

Question. Which of the given elements A, B, C, D and E with atomic number 2, 3, 7, 10 and 30 respectively belong to the same period?
(a) A, B, C
(b) B, C, D
(c) A, D, E
(d) B, D, E
Answer : B

Question. Which of the following statements about the Modern Periodic Table is correct:
(a) It has 18 horizontal rows known as Periods
(b) It has 7 vertical columns known as Periods
(c) It has 18 vertical columns known as Groups
(d) It has 7 horizontal rows known as Groups
Answer : C

Question. The most distinctive property of the noble gases is that they are:
(a) Unreactive
(b) Radioactive
(c) Metalloid
(d) Metallic
Answer : A

Question. The group number, number of valence electrons, and valency of an element with the atomic number 15, respectively, are:
(a) 16, 5 and 2
(b) 15, 5 and 3
(c) 16, 6 and 3
(d) 15, 6 and 2
Answer : B

Question. Which of the p-block elements are not representative elements?
(a) Alkali metals (I-A)
(b) Group-14 elements (IV-A)
(c) Group-18 elements (VIII-A)
(d) Halogens (VII-A)
Answer : C

Question. Element X forms a chloride with the formula XCl2, which is a solid with high melting point. X would most likely be:
(a) Si
(b) Al
(c) Na
(d) Mg
Answer : D

Question. Which of the following pairs has both members from the same period of the periodic table.
(a) Na – Ca
(b) Na – Cl
(c) Ca – Cl
(d) Cl – Br
Answer : B

Question. In the Modern Periodic Table, if an element with atomic number 'X' is an inert gas, then an element with atomic number (X-1) will be placed in:
(a) Group 16
(b) Group 17
(c) Group 15
(d) Group 18
Answer : B

Question. An element 'Z' has the electronic configuration 2, 8. Name the element 'Z' and determine its atomic number.
(a) Argon, 10
(b) Neon, 8
(c) Neon, 10
(d) Helium,10
Answer : C

Question. Which of the following forms the most stable gaseous negative ion?
(a) F
(b) Cl
(c) Br
(d) I
Answer : B

Question. which of the following elements are found in pitch blende?
(a) Actinium and protoactinium
(b) Neptunium and plutonium
(c) Actinium only
(d) Both (a) and (b)
Answer :  B

Question. How many periods and groups are present in the periodic table?
(a) 7 periods and 18 groups
(b) 8 periods and 7 groups
(c) 7 periods and 7 groups
(d) 8 periods and 8 groups
Answer :  A

Question. Which of the following statements is not a correct statement about the trends when going from, left to right across the periods of the 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.
Answer :  C

Question. Which of the following properties generally decreases along a period?
(a) Ionization Energy
(b) Metallic Character
(c) Electron Affinity
(d) Valency.
Answer :  B

Question.The electronic configuration of halogen is
(a) ns² np6
(b) ns² np3
(c) ns² np5
(d) ns²Answer
Answer :  C

Question. Which of the following is the correct order of the atomic radii of the elements oxygen, fluorine and nitrogen?
(a) O < F < N
(b) N < F < O
(c) O < N < F
(d) F < O < N
Answer :  D

Question. 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
Answer :  B

Question. Which group elements are called transition metals?
(a) Group number 1 to 2
(b) Group number 13 to 18
(c) Group number 3 to 12
(d) Group number 1 to 8
Answer :  C

Question. The element with atomic number 35 belongs to
(a) d – Block
(b) f – Block
(c) p – Block
(d) s – Block
Answer : C

Question. 14 elements after actinium is called
(a) Lanthanides
(b) Actinides
(c) d-block elements
(d) p-block elements
Answer : B

Question. The group number and period number respectively of an element with atomic number 8 is
(a) 6, 2
(b) 16, 2
(c) 6, 8
(d) 16, 4
Answer : A

Question. In the third period of the Periodic Table the element having smallest size is
(a) Na
(b) Ar
(c) Cl
(d) Si
Answer : B

Question. The increasing order of the atomic radii of elements Na, Rb, K, Mg is
(a) Na < K < Mg < Rb
(b) K < Na < Mg < Rb
(c) Na < Mg < K < Rb
(d) Mg < Na < K < Rb
Answer : C

Question. An element with atomic number will form a basic oxide _________.
(a) 7
(b) 17
(c) 14
(d) 11
Answer : D

Question. The correct order of the increasing radii of the elements Na, Si, Al and P is
(a) Si, Al, P, Na
(b) P, Si, Al, Na
(c) Al, Si, P, Na
(d) Al, P, Si, Na
Answer : B

Question. Which is not true about noble gases?
(a) They are non-metallic in nature
(b) They exist in atomic form
(c) They are radioactive in nature
(d) Xenon is the most reactive among these
Answer : C

Question. Identify the wrong sequence of the elements in a group
(a) Ca, Sr, Ba
(b) Cu, Au, Ag
(c) N, P, As
(d) Cl, Br, I
Answer : B

Question. Mendeleev predicted the existence of two elements and named them as eka-silicon and eka-aluminium. Identify the elements which took their position at later stage
(a) Si and Ge
(b) Si and Ga
(c) Ge and Ga
(d) Si and Al
Answer : C

Question. The element with atomic number 3 to 10 belong to the second period. Identify the most electropositive and most electronegative element. 
(a) F, Li
(b) Li, F
(c) Li, Ne
(d) Ne, Li
Answer : B

Very Short Answer Questions

Question. Did Döbereiner’s triads also exist in the columns of Newland’s Octaves? Compare and find out.
Answer : Yes, it exists in the Newland’s octave. It is Li, Na and K.

Question. What were the limitations of Newlands’ Law of Octaves?
Answer : • Newlands’ law was applicable only till calcium, after Ca, every eighth element did not possess properties similar to first.
• New elements discovered did not fit into the law.
• Wrong order of arrangement of elements was done, e.g. Co and Ni do not resemble halogen were found together in same slot, Fe being similar to Co and Ni was separated and kept in different slot.

Question. Besides gallium, which other elements have since been discovered that were left by Mendeleev in his Periodic Table? (any two)
Answer : Besides gallium, germanium and scandium have been discovered.

Question. Why do you think noble gases are placed in a separate group?
Answer : Noble gases are inactive, do not resemble other elements and all of them show same properties, hence they are grouped separately.

Question. Name two elements you would expect to show chemical reactions similar to magnesium.
What is the basis for your choice?
Answer : Calcium and barium.
Reason : (i) Both of them belong to same group as magnesium.
(ii) Ba and Ca has same valence electrons as Mg, and will show same properties as of magnesium.

Question. (a) Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?
(b) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?
Answer : (a) All these metals are highly reactive, they have same valence electrons i.e. 1 and can readily loose electrons to become positive ions.
(b) Helium and neon have completely filled outermost shell.

Question. By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristics?
Ga, Ge, As, Se, Be
Answer : Among the given elements Be will show maximum metallic characteristics as it belongs to extreme left of the Periodic Table.

Short Answer Questions

Question. (a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Answer : (a) All other elements have same valence electrons and their valency is 3.
(b) All are non-metals, they have same valence electrons i.e., 7 and their valency is 1, all of them gain electrons to form negative ions.

Question. The position of three elements A, B and C in the Periodic Table are shown below:

(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?
Answer : (a) ‘A’ is non-metal.
(b) ‘C’ is less reactive than ‘A’
(c) ‘C’ is smaller in size than ‘B’
(d) ‘A’ will form negatively charged ion — Anion

Question. How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?
Answer : The position of element depends upon its electronic configuration. The number of shells is equal to the period number. The valence electrons decides the group number in which it will be, elements with 1 valence electrons belong to group 1.
Elements with 2 valence electrons belong to group 2.

Question. Compare and contrast the arrangement of elements in Mendeleev’s Periodic Table and the Modern Periodic Table.
Answer :