Periodic Classificartion Of Elements
Class: 10 | Chapter: 5
Extra Questions & Answer
1. Phosphorus does not conduct electricity whereas lithium does why?Ans. Metals are good conductors of electricity and non - metals are poor conductors or insulators. Here phosphorus is a non - metal which don't allow electricity to pass through it but lithium is a metal and has tendency to pass electricity through it.
2. Write general electronic configuration of d-block elements?
Ans. General electronic configuration : (n - 1 )d 1 -10 ns 1-2.
3. Why iodine atom is larger in size in comparison to chlorine atom?
Ans. Iodine atom is larger in size becouse it has bigger atomic size than chlorine which is due to more shielding effect.
4. Why are the group 2 elements called alkaline earth metals?
Ans. Group 2 elements are called alkaline earth metals becouse their compounds like oxides and hydroxides are bases which can be dissolved in water , oxides are found in earth and these elements have metallic properties.
5. Arrange the following atoms in order of decreasing atomic radius: Na, Al, P, Cl, Mg
Ans. Na > Mg > Al > P > Cl
6. What is the atomic number of the element that would occupy, the position in row 7,column 17 of the periodic table?
Ans. The atomic number is 117.
7. Why are the elements of group 18 called zero valent?
Ans. The elements of group 18 are called zero valent becouse they zero valency due to completely filled shells. They don't have any tendency to combine with other elements.
8. If an element X is placed in group 14 , what will be the formula and the nature of bonding of it's chloride?
Ans. X is placed in group 14, its valency will be 4 . When it combine with chlorine, the formula of chloride will be XCl4 and bonding will be covalent becouse for group 14 elements , it's difficult to loose or gain 4 electrons so, it generally shares electrons.
9. Arrange the ions S2-, Cl -, K + and Ca2+ in order of decreasing size order.
Ans. Hint : More is the negative charge, more will be size.
S2-> Cl- >K + > Ca2+
10. Compare and contrast the arrangement of elements of in Mendeleev's Periodic Table and Modern Periodic Table.
Ans. Mendeleev's Periodic Table : 1. It was based on atomic mass.
2. There are 8 groups and subgroups like A and B were there.
3. Only 63 elements were there at that time.
4. It contained some gaps for future elements.
5. Noble gases were not included.
Modern Periodic Table : 1. It is based on atomic number.
2. It has 18 groups and nobsubgroups are present.
3. It has 118 elements.
4. No gaps are there.
5. Noble gas have separate group.
11. What are the merits and demerits of newland’s classification?
Ans. Merits of newland's classification : 1. It first told about the periodicity of the elements.
2. It gives relationship between properties and atomic masses of elements.
Demerits of newland's classification : 1. It is applicable only upto calcium (atomic no. 20) .
2. After the discovery of noble gases, places given in this classification got changed.
12. X and Y are two elements having similar properties and obey Newland’s law of octaves. How many elements are there in-between X and Y?
Ans. There are 6 elements in - between X and Y.
13. What is achievement of Dobereiner’s law of traids?
Ans. 1. He was the first person to classify the elements.
2. His classification made base for future arrangements.
3. He was able to group three elements of same properties.
14. Lithium, Sodium and potassium were put in the same group on the basis of their similar properties.What is the similarity in their properties?
Ans. 1. They all have similar outer electronic configuration.
2. They are metals.
3. They react in the same way like, they all form basic oxides.
15. State two reasons for rejecting law of octaves.
Ans. 1. It is applicable only upto calcium (atomic no. 20) .
2. After the discovery of noble gases, places given in this classification got changed.
16. Name four alkaline earth metals. To which group do they belong?
Ans. Berilium, Magnesium, Calcium and strontium. They belong to group 2.
17. What is called diagonal relationship?
Ans. Diagonal relationship : The similarity in the properties of definite pairs of diagonally adjacent elements in the second and third periods of the periodic table.
18. Define electron affinity.
Ans. Electron affinity : It is equal to the amount of energy released when an atom adds an electron to it to form a negative ion.
19. What is called electronegativity?
Ans. Electronegativity : It is the tendency of an element to attract shared pair of electrons in a bond.
20. (a) Name an alkali metal other than lithium, sodium and potassium.
(b) Name an alkaline earth metals other than calcium, strontium and barium.
(c) Name one halogen other than chlorine, bromine and iodine.
(d) Name a non-metal having properties similar to carbon.
(e) Name a rare gas other than neon, krypton and xenon.
Ans. (a) Rubidium (Rb)
(b) Magnesium (Mg)
(c) Fluorine(F)
(d) Silicon (Si)
(e) Argon (Ar)
21. State Mendeleev’s Periodic Law.
Ans. Mendeleev’s Periodic Law states that, “The properties of the elements are periodic function their atomic masses.”
22. Why are the elements sodium and chlorine in the same period of the Periodic table?
Ans. Sodium and chlorine are in third period of the periodic table becouse both have 3 shells in which they have their last electron.
23. How does the metallic character of elements vary in a (a) Group (b) Period?
Ans.(a) In Group : Metallic character of elements increases down a group becouse on going down in group, atomic size increases and hence tendency to loose electron increases.
(b) In Period : Metallic character decreases in a period becouse in period generally atomic size decreases and nucleus holds electrons more strongly so, it's difficult to loose electrons.
24. An element X lies in third period and group 17 . Find out (a) the number of valence ele trons in its atom, (b) Valency of the element X, (c) nature - metallic or nonmetallic, (d) name of the element.
Ans. (a) X lies in group 17 . So, no. of valence electrons will be 7.
(b) valency = 8 - 7 => 1
(c) it is non - metallic.
(d) Chlorine.
25. How does the atomic size vary in going from Na to Cl in periodic table?
Ans. Atomic size decreases in a period becouse in going from Na to Cl nuclear charge increases and hence attractive forces. As a result, shell shrinks.
26. How does the modern periodic law differ from Mendeleef's periodic law?
Ans. Mendeleev's Periodic Table : 1. It was based on atomic mass.
2. There are 8 groups and subgroups like A and B were there.
3. Only 63 elements were there at that time.
4. It contained some gaps for future elements.
5. Noble gases were not included.
Modern Periodic Table : 1. It is based on atomic number.
2. It has 18 groups and nobsubgroups are present.
3. It has 118 elements.
4. No gaps are there.
5. Noble gas have separate group.
27. Discuss the position of hydrogen in the Modern long form periodic table.
Ans. Hydrogen is placed in group 1 with alkali metals becouse it has atomic number 1 . It has only one electron in first shell or last shell that's why it resembles with both alkali metals and halogens in properties. Hence, Its position is controversial.
28. Why was the necessity of classifying the elements into certain groups felt?
Ans. Before the nineteenth century,the number of elements was less so, their individual study was easy but with the time, new elements were discovered, Study of these elements and their compounds became difficult.That's why it was felt that elements should be classified in certain groups.
29. Why did Mendeleef leave many gaps in his periodic table?
Ans. Mendeleef left some gaps in periodic table to accommodate future elements and he names them as eka - boron, eka - aluminium etc. All these elements were found later and have same properties as predicted by Mendeleef.
30. How does metallic character change in a group?
Ans. Metallic character of elements increases down a group becouse on going down in group, atomic size increases and hence tendency to loose electron increases.
31. Name the element with which sulphur should resemble in accordance with the law of octaves?
Ans. Oxygen
32. Element M forms a chloride with the formula MCl2 which is a solid with high melting point. To which group or the periodic table does the element 'M' belong?
Ans. It belongs to group 2.
33. Name the element which is
(a) most metallic
(b) most nonmetallic
Ans. (a) Francium
(b) Fluorine
34. What is meant by horizontal relationship between the elements in the periodic table?
Ans. In periodic table, groups and periods are present. Horrizontal rows are called periods.In periods, electrons are filled in the same valence shell.
35. Describe the basic character of the oxides if 3rd period elements across the period.
Ans. Basic charater of oxides decreases in 3rd period becouse basic character of oxides is related to metallic character of elements and in a period atomic size decreases and hence tendency to loose electrons decreases.
36. Calcium is an element with atomic number 20.
(a) Is it a metal or nonmetal?
(b) What is it's valency?
(c) Is it more or less reactive than Mg?
(d) What is formula of its chloride?
Ans. (a) It is a alkaline earth metal.
(b) valency is 2.
(c) It is more reactive than Mg, becouse metallic character increases down the group.
(d) It's formula of chloride will be CaCl2.
37. In period 3
(i) Which atomic is bigger, Na or Mg? Why?
(ii) Name the most metallic and nonmetallic element in period 3.
Ans. (i) Na is bigger than Mg becouse in a period size decreases.
(ii) Most metallic element is Na and Non - metallic element is Chlorine.
38. By which common name are the elements of Group 1 and Group 17 called?
Ans. Group 1 elements are called alkali metals and Group 17 elements are called halogens.
39. An element E belongs to the second period and Group 13.Write the formula of its oxide.
Ans. E2O3.
40. What is meant by atomic radius? How does it vary down the group and why? How does it vary along a period and why?
Ans. Atomic radius : The distance from the centre of the nucleus to the outermost shell of electrons in an isolated atom.
In a group atomic radius increases becouse of addition of a new shell at each new element.
In a period atomic radius decreases becouse of increase in nuclear charge and attractive forces.