CBSE Class 11 Chemistry Periodic Classification Of Elements Worksheet

More Questions for Chemistry Periodic Classification Of Elements

Question. Group-2 Metals are referred to as:
(a) Alkali Metals
(b) Alkaline earth Metals
(c) Chalcogens
(d) Halogens
Ans. B

Very Short Answer Type Questions

Question. Explain the basic character of oxide of elements down the group and across the period.
Answer : The basic nature decreases across the period. It changes from basic to acidic. The basic nature increases down the group.
These variations in acidic and basic nature of oxides can be related to electronegativity of the element. As the electronegativity of the element decreases down the group the basic character of the oxide increases.

Question. Write two achievements of Mendeleev’s periodic table.
Answer : (i) It could classify all the elements discovered at that time.
(ii) It helped in discovery of new elements.

Question. Out of lithium and potassium, which will have higher metallic character and why?
Answer : Potassium will have stronger metallic character than lithium because as we move from top to bottom in a group, the size increases which increases ease of liberation of electron.

Question. Where would you expect to find the element with atomic number 18 in the periodic table?
Answer : The element will bein-18th group and in the 3^rd period of the periodic table.

Question. An element belongs to group 13 and period 3, name the element and give its valency.
Answer : The element is Aluminium.
The valency = 3

Question. An element X belongs to group 17 and element Y belongs to group 1. What type of bond will they form?
Answer :

Question. What is the valency of magnesium with atomic number 12 and nitrogen with atomic number 7?
Ans. Magnesium, atomic number = 12
Electronic configuration = 2, 8, 2
∴ Valency = 2
Nitrogen, atomic number = 7
Electronic configuration = 2, 5
∴ Valency = 3

Question. What happens to the electropositive character of elements as we move from left to right of the period in the Periodic Table?
Answer : On moving from left to right in a period, the electropositive character decreases as the tendency to lose electrons decreases. 

Question. What are halogens? Where are they located in the Periodic Table?
Answer : Halogens are those elements which react with metals to form salts. They are present in 17th group of the Periodic Table.

Question. (a) Why do we classify elements?
(b)What were the two criteria used by Mendeleev in creating his periodic table.
(c)Why did Mendeleev leave some gaps in his periodic table?
(d)In Mendeleev’s Periodic table, why was there no mention of Noble gases like He, Ne and Ar?
Answer : (a) classification of elements helps in systematic study of the properties if elements and in understanding and remembering the properties of elements.
(b) The two criteria are increasing order of atomic mass and similarity in the properties of elements.
(c) Mendeleev left gap in his periodic table for the undiscovered elements like Germanium and Gallium
(d) There was no mention of gases like He, Ne and Ar as they were not known at that time, and were discovered much later

Short Answer Type Questions

Question. Why Mendeleev could not assign fixed position to hydrogen in the table?
Answer : (a) Hydrogen resembles alkali metal, i.e. like alkali metals it combines with halogen, oxygen and sulphur to form compounds with similar formula as alkalis.
(b) Like halogen, hydrogen also exists as diatomic molecule and combine with metal and non-metals to form covalent compounds.

Question. State two characteristics of groups.
Answer : All the elements in a group have the following characteristics:
(a) All element in a group show same number of valence electrons, hence show similar properties.
(b) As we move top to bottom in a group the atomic radius goes on increasing and there is a slight gradation in properties.

Question. The number of electrons goes on increasing in the outer shell as we move from left to right in a period, why does the atomic size goes on decreasing?
Answer : In a period all elements have same number of shells. As we move from left to right in a period the number of electrons goes on increasing at the same time the number of protons also goes on increasing therefore attraction force of nucleus increases and pulls the valence electrons i.e. the outermost shell towards the nucleus and hence the size of atom goes on decreasing.

Question. What happens to the non-metallic character as we move from top to bottom in a group?
Answer : The non-metallic character decreases as we move from top to bottom in a group as the tendency to gain electrons decreases down the group.

Question. Why are noble gases placed in a separate group?
Answer : All noble gases show same valency i.e. ‘0’, all of them are inert gases, the chemical properties are same and hence they are placed in same group.

Question. State the difference between Modern Periodic Table and Mendeleev’s Periodic Table.
Answer :

Mendeleev’s Periodic Table Modern Periodic Table
1. It is based on atomic mass. 1. It is based on atomic number.
2. It has 8 groups and 7 periods. 2. It has 18 groups and 7 periods.
3. No place for isotopes. 3. Isotopes were not considered.

Question. How does electronic configuration helps us to locate the position of element in the Periodic Table?
Answer : The electronic configuration of an atom conveys the valence electrons and number of shells. Valence electrons helps in detecting the group number.
Number of shells in an atom tells the period to which it belongs.

Question. Why does the reactivity of metals increases and that of non-metals decreases as we move down the group?
Answer : Reactivity of metals depends on the tendency to lose electrons. If the atomic size increases, the valence electrons are easily removed thereby forming positive ion. In case of metals the atomic size increases as we move down the table. Reactivity of non-metals depends on the tendency to gain electrons. As we move down the group, the tendency to gain electrons decreases because the atomic size increases, the nuclear force decreases.

Question. For the following given elements predict the;
(a) Valency
(b) Period number
(c) Group number
Na (11), Al(13), Cl(17), K(19)
Answer :

Question. Lithium, sodium potassium belong to same group called alkali metals. Why?
Answer : Lithium, sodium and potassium have same valence electron i.e. 1, hence they belong to same group. The group is called alkali metals group because all these elements form oxides which dissolve in water to form alkali.

Long Answer Type Questions

Question. The atomic number of element X is 17 predict its
(a) Physical state.
(b) Name of element.
(c) Formulae of its compound with hydrogen.
(d) Metal or Non-metal.
(e) Formulae of its molecule.
Answer :  Atomic number of X = 17.
Electronic configuration = 2, 8, 7
(a) Physical state → Gas
(b) Chlorine
(c) HCl
(d) Non-metal
(e) Cl₂

Question. Give all characteristics of group.
Answer : Characteristics of a group:
(a) Valence electrons → All elements show same valence electrons in a group.
(b) Valency → Valency of all the elements remains the same in a group.
(c) Atomic size → The atomic size goes on increasing down the group.
(d) Metallic character → In case of metals the metallic character increases down the group.
(e) Non-metallic character → In case of non-metals the non-metallic character decreases down the group.

Question. You are given five elements with some description of each element, place them in the Modern Periodic Table.
(a) Essential for breathing and burning.
(b) Inactive, two electrons in the outermost shell.
(c) Atom has same number of protons, electrons and neutrons, used in fertilizer industry.
(d) Number of neutrons, protons are same used in building our bones.
(e) This element form the hardest naturally occurring substance as allotrope.
Answer :

Question. (a) What are ‘groups’ and ‘periods’ in the Periodic Table?
(b) Two elements M and N belong to groups I and II respectively and are in the same period of the Periodic Table. How do the following properties of M and N vary?
(i) Sizes of their atoms.
(ii) Their metallic characters.
(iii) Their valencies in forming oxides.
(iv) Molecular formulae of their chlorides. 
Answer : (a) The vertical column in the Periodic Table are called ‘groups’, the horizontal rows in the table are called periods.
(b) (i) ‘M’ and ‘N’ belong to the same period but group I and II respectively. N is smaller than M as the atomic size decreases on moving from left to right across the Periodic Table.
(ii) M is more metallic than ‘N’ because metallic character decreases from left to right as tendency to lose electrons decreases due to decrease in atomic size.
(iii) The valencies of M and N are 1 and 2 respectively, valency across the period first increases then decreases.
(iv) MCl and NCl₂.

Question. (a) Why do we classify elements? 
(b) What were the two criteria used by Mendeleev in creating his Periodic Table?
(c) Why did Mendeleev leave some gaps in his Periodic Table?
(d) In Mendeleev’s Periodic Table, why was there no mention of Noble gases like Helium, Neon and Argon?
(e) Would you place two isotopes of chlorine Cl-35 and Cl-37 in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? Justify your answers.
Answer : (a) Classification is done to study the properties of elements conveniently.
(b) Increasing order of atomic mass and similarity in chemical properties i.e. the nature of oxide and hydride formed.
(c) The gaps were left for undiscovered elements then.
(d) Noble gases were not invented at that time.
(e) Cl-35 and Cl-37 will be kept in the same slot as their chemical properties are same.

Question. (a) Why did Mendeleev left gaps in his Periodic Table? 
(b) State any 3 limitations of Mendeleev’s classification.
(c) How does electronic configuration of atoms change in period with increase in atomic number?
Answer : (a) Mendeleev left some gaps for undiscovered elements, because he predicted that there would be such elements which will fit in the gaps in future. He also predicted the properties of these elements.
(b) 3 limitations are:
(i) Position of hydrogen was not justified.
(ii) Increasing order of atomic mass could not be maintained.
(iii) Isotopes were not given separate place as they have different atomic mass.
(c) In a period the valence electrons goes on increasing from left to right as the number of shells is same.

Q1. Who gave Law of Trade?

Q2. Name the scientists who first arranged then known elements in order of increasing atomic weights.

Q3. Name the scientist who got Davy medal in 1887 by the Royal Society London and why?

Q4. Explain Leather Mayer’s contribution in classification of elements.

Q5. What do you understand by periodicity for the elements?

Q6. Why it is not possible to measure the absolute value of the atomic radius of an element?

Q7. Based upon the nature of Bonding, what are the different forms of atomic radii?

Q8 Define each of one of atomic radii with example and compare them?

Q9. Explain variation of Atomic radii a long a period and down the group.

Q10. Out of Li⁺, Be⁺² and B⁺³, which has the smallest ionic radius & why?

Q11. Which of the following are iso-electronic in nature?
(i) O^2- (ii) Na (iii) F (iv) S^2- (v) Mg²⁺ (vi) Al ⁺³

Q12. Select the species with smallest size in the following:- (a) I, I⁺, I^- (b) N, O, P (c) F, Cl, Br

Q13. Among the elements with At No. 9, 12, 36 identify the element which is (a) highly electronegative (b) an inert gas in nature (c) highly electropositive in nature.

Q14. Arrange the following in increasing order of the property indicate:-
(i) F, Cl, Br and I (negative electron gain enthalpy) (ii) Mg⁺², O^2-, Na⁺, F-, and N^3- (ionic size).
(iii) Mg, Al, Si and Na (Ionization Enthalpy) (iv) Br⁺, Br and Br^- (size) (v) GN, O and F (Ionization Enthalpy)

Q15. Would you expect the Ionization Enthalpies of 2 isotopes of same element to be same or different? Justify your answer?

Q16. Write the general e-configuration of S, P, d and f-block elements?

Q17. Argon (Atomic mass = 39.94) has been placed before Potassium (At mass 39.10) in the Periodic table. Why?

Q18. Explain (a) why do Ionization enthalpies decrease down a gp.
(b) Why do Ionization Enthalpies increase as we move along the period?

Q19. From each set, choose the element with largest Ionization enthalpy and explain your answer:-
(a) F, O, N (b) Mg, P, Ar (c) B, Al, Ba

Q20. Predict the position of the element in the periodic table satisfying the configuration (n-1) d1ns2 for n=4.