Class 10: Classification of elements

 

UNIT 14: CLASSIFICATION OF ELEMENTS

Multiple Choice Question [1 mark each]

1.    Which of the following is correct about the modern periodic law?

a) It is based on atomic number               b) It is based on atomic size

c) It is based on atomic mass                   d) It is based on valence electron

2.    Which of the following block do alkali metals belong to?

a) f-block                b) d-block               c) p-block               d) s-block     

3.    Among the following which one is highly reactive?

a) Sodium                b) Lithium               c) Potassium           d) Magnesium

4.    Which of the following element is least reactive?

a) Lithium               b) sodium                c) Potassium           d) Rubidium

5.    Which of the following element is electronegative?

a) Magnesium         b) Iodine                 c) Calcium              d) Gold        

6.    What are f-block elements called?

a) halogens                        b) representative elements 

c) transitional elements      d) inner transitional elements

7.    How many groups are there in modern periodic table?

a) 7                         b) 8                         c) 18                       d) 32

8.    What is the electronic configuration of copper?

a) 1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d⁹              b) 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹, 3d¹⁰

c) 1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰             d) 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹, 3d⁹

9.    In which group do alkaline earth metals belong to?

a) group 1                b) group 2               c) group 3               d) group 4

10. In which group of Modern Periodic Table, noble gases are placed?a

a) group 1                b) group 7               c) group t8r             d) group 18

11. Who proposed Modern periodic Table?

a) Henry Moseley    b) D.I. Mendeleev   c) Antonio Lavoisier                 d) John Newland

12. What is the valency of the element 1s², 2s², 2p⁵?      

a) 2                         b) 5                         c) 7                         d) 0

13. What are the horizontal rows of the modern periodic table called?

a) group                  b) period                 c) block                  d) family

14. Which of the following element is metalloid?

a) Al                       b) S                         c) Na                      d) Si

15. Which of the following is more electronegative?

Oxygen                   b) carbon                 c) Fluorine              d) Chlorine`

16. a

Answers: 1(a), 2(d), 3(c), 4(a), 5(b), 6(d), 7(c), 8(b), 9(b), 10(d), 11(a), 12(c), 13(b), 14(d)

 

Very Short Answer Question [1 mark each]

1. What is the name of the element of atomic number from 58 to 71?

The names of the elements from atomic number 58 to 71 is Lanthanides.

2. Write down the position of metals and non-metals in the modern periodic table?

Metals are kept on the left side and non-metals are kept on right side of the modern periodic table.

3. In which group of modern periodic table alkaline earth metal and halogen are kept?

Alkali earth metals are kept in group IIA and halogens are kept in group VIIA.

4. State the law of modern periodic table.

Modern periodic law states that the physical and chemical properties of elements are periodic function of their atomic number.

5. In which group of the modern periodic table do alkali metals and inert gas lie?

Alkali metals lie in group IA and inert gases lie in group 0 (zero).

6. Which block of modern periodic table makes acidic oxide?

Generally, p-block of the modern periodic table makes acidic oxide.

7. Write the names of two elements belonging to group 17 of the modern periodic table.

The names of two elements belonging to group 17 of the modern periodic table are Fluorine and Chlorine.

8. What are the maximum number of electrons that can accommodate in P and f sub-shell?

The maximum number of electrons that can be accommodated in P sub-shell are 6 and f sub-shell are 14.

9. Write the electronic configuration of Ca on the basis of sub-shell.

The electronic configuration of Ca on the basis of sub-shell is:₂₀Ca = 1s², 2s², 2p⁶, 3s², 3p⁶, 4s².

10. What is periodic table?

The table formed by arranging the elements having similar physical and chemical properties by following the periodic rule is called periodic table.

11. What is electronic configuration?

The distribution of electrons in different orbitals of an atom is called electronic configuration.

12. What is duplet state? Write with one example.

The state of an atom in which the outermost shell of the atom has tendency to accommodate two electrons only is called duplet state. Example : Helium atom

13. What is octet state? Write with example.

The state of an atom in which the outermost shell of the atom has tendency to accommodate eight electrons only is called octet state. Example : neon, argon atoms.

14. What are alkali metals? Give one example.

Highly reactive metals of group 1 of the modern periodic table are called alkali metals. Example sodium, potassium, etc.

15. What are alkaline earth metals? Give one example.

The reactive metals of group 2 of modern periodic table are called alkaline earth metals. Examples: Magnesium, calcium, etc.

16. What are halogens? Give one example.
17. Halogens are the elements of group 17 having seven electrons in their valence shell. Example: Fluorine, Chlorine.
18. What are inert gases? Give example.

The elements of group 18 having completely filled valance shell and do not take part in chemical reaction are called inert gases or Noble gases.

19. What are metalloids? Give example.

The elements having properties of both the metals and non-metals are called metalloids. Example: silicon, arsenic, etc.

20. What are the elements called that lie between group 2 and group 13?

The elements that lie between group 2 and group 13 are called transitional elements or d-block elements.

21. Write the electronic configuration of Aluminium and Potassium in terms of sub shell.

The electronic configuration of Aluminium and potassium on the basis of sub-shell are:

₁₃Al = 1s², 2s², 2p⁶, 3s², 3p¹                ₁₉K = 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹

22. What are transitional elements?

The metals which are present in between the group IIA and IIIA in the periodic table i.e. IB to VIIB and VIII bearing last valence electrons at the d-sub shell are called transitional metals. They are collectively called d block elements.

23. In what group do magnesium and nitrogen belong in the modern periodic table?

Magnesium belongs to group IIA and Nitrogen belongs to group VA in the modern periodic table.

24. State Mendeleev's periodic law.

Mendeleev's periodic law states that the physical and chemical properties of elements are periodic function of their atomic weight.

25. What is modern periodic table?

Modern periodic table is a chart obtained by arranging different elements with their increasing atomic number so that elements having similar physical and chemical properties can come to lie within the same group.

26. Write the names of the groups, in which very active metals and very active non-metals are placed in modern periodic table.

Very active metals are placed in group IA and very active non-metals are placed in group VIIA in the modern periodic table.

27. In what group do magnesium and oxygen belong in the modern periodic table?

Magnesium and oxygen belongs to group IIA and VIA respectively in the modern periodic table.

28. In which group of the modern periodic table are placed the very reactive metal and halogens?

Very active metals are placed in group IA and halogens are placed in group VIIA in the modern periodic table.

29. What do you mean by Lanthanides?

Lanthanides are the first series elements of f block having atomic number 58 to 71.

30. In which period potassium and calcium lie in the modern periodic table?

Potassium and Calcium lie in 4^th period in the modern periodic table.

31. Give the name and group of an element whose electronic configuration is 1s², 2s², sp⁶, 3s², 3p⁶, 4s¹.

The name of the element having electronic configuration 1s², 2s², sp⁶, 3s², 3p⁶, 4s¹ is Potassium and group is IA.

32. Write down the two factors that determine the reactivity of the elements.

The two factors that determine the reactivity of the elements are size of the atoms and number of valence electrons.

33. How many periods and groups are there in modern periodic table?
34. There are 7 periods and 18 groups in modern periodic table.

 

Short Answer Questions [2 marks each]

1. Write any two features of Modern periodic table.

Two features of modern periodic table:

a)     The modern periodic table consists of 7 horizontal rows called period and 18 vertical column called group.

b)    The elements are divided into 4 blocks on the basis of sub-shell.

2. What happens to the reactivity of metals from left to right in 3^rd period of modern periodic table? Why?

The reactivity of metals decreases from left to right in the 3^rd period of modern periodic table. This is because when we move from left to right in the period, the nuclear charge of atoms of elements increases. Due to greater nuclear charge, the valance electrons are more tightly held by the nucleus. So, the tendency to lose electron decreases and hence reactivity of metal also decreases.

3. Atomic size of inert gases do not affect inertness, why?
4. Inertness of the inert gases is due to the completely filled valance shell not the atomic size. As a result they do not take part in chemical reaction whether the atomic size smaller or larger.
5. Write two methods for increasing the rate of chemical reaction.
6. Two methods of increasing the rate of chemical reaction are:

a)     By increasing the temperature of reactants.

b)    By making the reactants molten or solution.

7. What difference in the chemical reactivity of metals of second period occur while moving from left to right in the modern periodic table? sodium is called a metal, why?
8. Sodium is called a metal because it has tendency to lose electron and acquire positive charge.
9. In which group of modern periodic table, elements having atomic number 9 and 17 belong? Which one is more reactive and why?

Element having atomic number 9 and 17 belong to group VIIA. Elements having atomic number 9 (Fluorine) is more reactive than 17 (Chlorine). This is because both are electronegative elements and they have the tendency to gain electrons to be stable. Being smaller in size Fluorine gains electron more easily than chlorine.

10. What is the relationship between size of atoms and reactivity in case of non-metals?

The reactivity of non-metals decreases with the increase in atomic size of non-metal. This is because as the atomic size increases there is a decrease in nuclear attraction on the valence shell and hence the incoming electrons can not be hold firmly. This causes the reduction in reactivity of non-metal.

11. Why reactivity of group VIIIA elements are not affected by their atomic size? (REPEATED)
12. Between magnesium and calcium, which element is more reactive? Give reason.

Calcium is more reactive than Magnesium although both belong to group IIA of the periodic table. This is because as we move down the group atomic size increases and the valence electrons are loosely bound. Thus Calcium is more reactive than Magnesium.

13. How many electrons do d-sub shell of periodic table maximum have? Why are the elements of group IA of this table called alkali metals?

d- sub shell of the periodic table has maximum number of 10 electrons. The elements of group IA of this table is called alkali metals because they for water soluble base alkali when react with water.

14. Why do reactivity of elements increases on moving from top to bottom in group IA of the modern periodic table?

Group I A elements are electro-positive in nature. They have the tendency to lose 1 electron to be stable. On moving from top to bottom, the atomic size increases due to which outermost electrons are loosely held by nucleus and hence tendency to lose electron increases in successive steps downwards in group IA.

15. Answer the following questions on the basis of given table.

Elements	Electronic configuration
A	1s2	2s2 2p6	3s1
B	1s2	2s2 2p6	3s2 3p5
C	1s2	2s2 2p6	3s2 3p6

i)               Write the names of the elements A, B and C

Element A is Sodium, B is Chlorine and C is Argon.

ii)             To which block does the element C belong? Mention its one chemical nature.

C belongs to P-block of the periodic table. Its one chemical nature is that it is inert gas and it does not take part in any chemical reaction.

16. Write any two characteristics of modern periodic table.

(REPEATED)

17. Fluorine is more reactive than chlorine, why?

Similar to 27.

18. Hydrogen is kept with metal even it is non-metal. Give reason. Which one is more reactive between fluorine and Chlorine. Why?

Hydrogen is kept with metal even it is non-metal. This is because it has atomic number one and it has one electron in its valence shell. Similar to 27.

19. Write the electronic configuration of Aluminium and Potassium in terms of sub-shell.

REPEATED

20. Distinguish between modern periodic table and Mendeleev's periodic table in two points. Elements of Group VIIIA are called noble gas. Why?

The difference between modern periodic table and Mendeleev's periodic table are:

Mendeleev's periodic table	Modern periodic table
(1) The elements are arranged in order of increasing atomic weight	(1) The elements are arranged in order of increasing atomic number.
(2) There were only 63 elements.	(2) There are 109 elements
(3) It is divided into 4 blocks on the basis of sub-shell.	(3) It is not divided into any blocks.

 

21. What is the change in the chemical reactivity of very active non-metals when their atomic size increases?

When the atomic size increases, the chemical reactivity decreases in case of non-metals. This is because non-metals gain electron to acquire nearest noble gas configuration. Lesser the size of atom, more easily to gain the electrons. Thus, the reactivity of very active non-metals decreases  as we move down the group.

22.  Elements of group VA, VIA and VIIA are less reactive as we go down in the group of modern periodic table?

Elements of Group VA, VIA and VIIA are electronegative in nature. They have the tendency to gain electron to be reactive. As we move down the group in VA, VIA and VIIA, the atomic size increases. As a result, the nuclear attraction on outermost orbit decreases and thus tendency to gain electron decreases.

 

23. In which periodic table are the elements arranged on the basis of increasing atomic number? Why are group VIIA elements called halogens?

The elements are arranged on the basis of increasing atomic number in modern periodic table. Group VIIA elements are called halogens because they reacts with highly reactive metals of S block to form their salts. The salts thus formed are called hallides.

24. Write any two reasons for keeping hydrogen in group IA in the periodic table.

Two reasons for keeping hydrogen in group IA in the periodic table are:

i) It has one electron in its valence shell.

ii) It lose electron like the elements of IA to be electropositive radical.

25. Write down the electronic configuration of the elements which lies in second period and sixth group of modern periodic table based on sub-shells.

The electronic configuration of the element that lies in second period and sixth group of modern periodic table based on the sub-shell is:

Oxygen (₈O) = 1s² 2s² 2p⁴

26. In which periodic table elements are arranged on the basis of increasing atomic number. Write down any two characteristics of this table.

REPEATED.

27. Why is Potassium more reactive than sodium although they belong to same group IA?

Potassium is more reactive than Sodium although they both belong to group IA because Potassium is larger in size. Outermost electrons are less tightly held in Potassium than Sodium. As a result Potassium loses one electron from its valence shell more easily than Sodium. Hence, Potassium is more reactive than sodium.

28. Alkali metals are more reactive, why?

Alkali metals have one electron in their valence shell; hence, they can easily lose the electron so as to achieve nearest noble gas configuration. So, they are more reactive.

29. Write the electronic configuration of sodium, potassium and chlorine on the basis of sub-shell.

The electronic configuration of Sodium, Potassium and Chlorine on the basis of Subshell are:

₁₁Na = 1s², 2s², 2p⁶, 3s¹

₁₉K = 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹

₁₇Cl = 1s², 2s², 2p⁶, 3s², 3p⁵

30. In what group noble gases, most reactive non-metals, most reactive metals and metalloids are placed?

Noble gases are placed in group 0 group, most reactive non-metal in group VIIA, most reactive metals in group IA and metalloids in group VIA in modern periodic table.

31. Repeated
32. Write down two factors that determine the reactivity of elements.

Two factors that determine the reactivity of elements are:

i)               Number of electrons present in the valence shell.

ii)             Atomic size.

33. In what group do Calcium and Chlorine belong in the periodic table? Write with reason the chemical reactivity of these groups when going from top to bottom.

Calcium belongs to 4th period and Chlorine belongs to 3rd period in the periodic table. The chemical reactivity of group IIA (Calcium) increases while going from top to bottom because their atomic size increases and it become easier to lose electrons. The chemical reactivity of group VIIA (Chlorine) decreases because the atomic size increases and the tendency to gain electrons decreases.

34.           How is chemical reactivity of groups where Magnesium and oxygen belong when going from top to bottom? Write with reason.

On going from top to bottom, the chemical reactivity of Magnesium group (IIA) increases because the atomic size increases and hence the tendency to lose electron increases but in the group of oxygen (group VIA), the chemical reactivity decreases while moving from top to bottom because the atomic size increases and the tendency to gain electrons decreases.

1. Write the balanced chemical equation for the chemical reaction between any one of very active metal and very active non-metal.

The balanced chemical equation for the chemical reaction between any one very active metal and very active non-metal is:

Na       +                      Cl₂                                                        NaCl

very active metal                       Very active non-metal

35.  
36. Why is Lanthanides kept separately in the periodic table?

Lanthanides are kept separately in the periodic tale because the elements of Lanthanides do not show similar properties with other elements (elements of S, P and d block)

Long Answer Questions [4 marks each]

1. Write the differences between S and P block.

The differences between S and P block are:

S block	P-block
i) There are 2 groups in S block	i) There are 6 groups in P block
ii) Elements of S block are metals	ii) Elements of P-block are mostly non-metals.
iii) S-block elements have S-sub shell as the last orbital.	iii) Elements of P-block have P-sub shell as the last orbital.
iv) The reactivity of the elements goes on increasing while moving down the in the group in this block.	iv) The reactivity of the elements generally goes on decreasing while moving down the in the group in this block.
v) The melting and boiling point decreases moving down the group in s-block.	v) The melting and boiling point increases moving down the group in s-block.

 

2. Study the given table and answer the following questions:

Elements	Electronic configuration
A	1s2 2s2 2p5
B	1s2 2s2 2p6 3s2
C	1s2 2s2 2p6 3s2 3p5

i)      Write the valency and block of element B.

The valency and block of element B are 2 and S block respectively.

ii)    Why A is more reactive than C?

iii)  A is more reactive than C because the atomic size of A is smaller than C. Its nuclear attraction on outermost orbit is more than C. Thus, it can attract incoming electrons more effectively to acquire nearest noble gas configuration than element C.

iv)     Write the balanced equation of the chemical reaction between B and C.

The balanced chemical equation of the chemical reaction between B and C is:

Mg + Cl₂                                             MgCl₂

3. Answer the following questions on the basis of the given table.

Name of element	X	Y	Z
Electronic configuration	1s2 2s2 2p6 3s1	1s2 2s2 2p6 3s2 3p5	1s2 2s2 2p6 3s2 3p6

i)               Write the names of elements indicated by X and Y.

The names of elements indicated  by X is Sodium and Y is Chlorine.

ii)             Write the block of the element X and Y.

The block of X and Y are S-block and P-block respectively.

iii)           Write the valency and chemical nature of Z.

The valency of Z is 0(zero) and its chemical nature is that it is inert gas and it does not take part in any chemical reaction.

iv)            Write a balanced chemical reaction between X and Y.

The chemical reaction between X and Y is:

2X + Y₂                                               2XY

4. Answer the following question if atomic number of Potassium is 19.

i)               Write the electronic configuration of it on the basis of sub-shell.

The electronic configuration the basis of sub-shell is:₁₉K = 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹

ii)             Write its group and period in periodic table.

Its group is IA and period is 4^th in periodic table.

iii)            What is it’s valency? Why?

Its valency is 1 because it has 1 electron in its valence shell which can easily be lost to other atom to acquire nearest noble gas configuration.

iv)            Write a balanced equation that takes place between the chemical reaction of potassium and oxygen.

The balanced chemical reaction take takes place between potassium and oxygen is:

K + O₂                                     K₂O

5. Which group of the modern periodic table is shown in the given table and what is the name given for metals in this group? What happens to the chemical reactivity while going top to bottom? Why?

Be

Mg

Ca

Sr

Group IIA of the modern periodic table is shown in the table and the name given for the metals in this group is Alkaline earth metals. While going from top to bottom, the chemical reactivity increases because they are electropositive metals and they have tendency to lose electrons to acquire nearest noble gas configuration. On moving down the group atomic size increases and the tendency to lose electrons increases. As a result they become more reactive on moving from top to bottom.

6. Element of which group in the periodic table are shown in the given table? Which element is most reactive among them? Give reason. Write the electronic configuration of Na and K on the basis of sub shell.

LI

Na

K

Elements of Group IA are shown in the given table. K is more reactive among them. This is because atomic size of K is larger than Na and Li. As a result, K loses electron more easily than Na and Li. The electronic configuration of Na and K are:

₁₁Na = 1s², 2s², 2p⁶, 3s¹

₁₉K = 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹

7. Study the given table and answer the following questions.

Elements	Electronic configuration
P	1s2 2s2 2p6 3s1
Q	1s2 2s2 2p6 3s2 3p6 4s1
R	1s2 2s2 2p6

(i)    What is the valency of element R?

The valency of element R is 0.

(ii)  Which is more active between P & Q, Why?

Q is more active between P and Q because both P and Q are have 1 electron in their valence shell. Being larger in atomic size Q loses electrons more readily than P. Hence, Q is more active between P and Q.

(iii)                  To which group of modern periodic table do elements P and Q belong to?

(iv) Elements P and Q belongs to group 1 of the modern periodic table. 

(v)  What is the common name given to element R? Why?

8. Which group elements of the periodic table are kept in a given table? What happens to the chemical reactivity of elements from top to bottom in the given table? Why? What is the name of the group and why?

F

Cl

Br

I

Elements of Group VIIA are shown in the given table. The chemical reactivity of these elements decreases from top to bottom in the given table. This is because these elements are electronegative in nature. As we move down the group, the atomic size increases and the tendency to gain electron decreases. Hence, the reactivity of the elements decreases on moving down the group. The name of this group is halogen because they have strong tendency to react with metals and form their respective salts. The word ‘halo’ means salt and ‘gen’ means to produce in Greek language.

9. Answer the following question according to the electronic configuration.

A = 1s² 2s² 2p²                        B = 1s² 2s² 2p⁴

i)      Write the names of the compound formed by the combination of these elements. Also write the molecular formula and the type of bond formed by the combination of these two elements.

The name of the compound formed by the combination of these elements is Carbon dioxide. The molecular formula is CO2 and the type of bond formed by the combination of these two elements is covalent bond.

ii)    Write down the balanced chemical when the above formed compound is dissolved in water.

The balanced chemical equation when the above formed compound (CO2) is dissolved in water is:

CO₂ + H₂0                         H₂CO₃

iii)   Write down the group, period and block of element A in the periodic table.

The group of element A is group IVA, period 2nd and block is P-block.

10. The electronic configuration of two elements are given below. Name these elements. Write the molecular formula of the compound formed by the combination of these elements. Write the chemical equation for the reaction between these two elements. Write the chemical equation for the chemical reaction takes place when thus formed compound is treated with hydrochloric acid?

i) 1s² 2s² 2p4               ii) 1s² 2s² 2p⁶3s¹

The elements are oxygen and Sodium. The molecular formula of the compound formed by the combination of these elements is: Na₂O.

The chemical reaction between these two elements is :Na + O₂                                                Na₂O

The chemical equation when the above formed compound is treated with Hydrochloric acid.

Na₂O + 2HCl                                   2NaCl + H₂O

11. Answer the following questions from the given table.

A	1s2	2s2 2p6	3s1
B	1s2	2s2 2p6	3s2 3p5
C	1s2	2s2 2p6	3s2 3p6

 

i)      Write the names of elements indicated by A and B.

The name of element indicated by A is Sodium and B is Chlorine.

ii)    Write the block of A and C.

The block of A is S and C is P block.

iii)  Write the name of element indicated by C and its chemical nature.

The name of element indicated by C is Argon and its chemical nature is that it is inert gas and it does not take part in chemical reaction.

iv)   Write the balanced chemical equation between element A and B with its type.

The balanced chemical equation between element A and B is:

2Na + Cl₂                          2NaCl

The type of reaction is Additional or Combination reaction.

 

12. Answer the questions on the basis of the electronic configuration of the elements given below.

A - 1s² 2s² 2p⁶3s¹            B-1s² 2s² 2p⁶3s²3p⁵

i)   Write the valencies of above elements.

The valency of both the above element is 1.

ii)  Which of the above element is electronegative? Why?

Element B is electronegative. It is because its atom gains one electron from other atom and become negatively charged.

iii)           Write the molecular formula of the compound formed by the combination of these elements.

The molecular formula of the compound formed by the combination of these two elements is Nacl

iv)Write an equation for the reaction taking place between the aqueous solution of the compound formed above and silver nitrate solution.

The equation for the reaction taking place between the aqueous solution of the compound formed above and silver nitrate is:AgNO₃ + NaCl                                        NaNO₃ + AgCl

13. What Atomic number of A and B are 8 and 12 respectively. Answer the following question on the basis of that:

i)      Give the electronic configuration of elements A and B.

Electronic configuration of A and B are: A - 1s² 2s² 2p⁴           B-1s² 2s² 2p⁶3s²

ii)    State the block of periodic table in which these elements belong to.

A belongs to P block and B belongs to S block

iii)  Write down the molecular formula of the compound formed by the combination of these elements.

The molecular formula of the compound formed  by the combination of these elements is MgO.

iv)   Which of them is electropositive and Why?

Between A and B element B is electropositive because it has two electrons in its valence shell which is lost to other atoms to acquire nearest noble gas configuration.