CBSE Class 10 Science Chapter 5 Periodic Classification Of Elements Short Answer Questions

CBSE Class 10 Science Chapter 5 Periodic Classification Of Elements


Periodic classification of elements

CBSE Class 10 Science Chapter 5 Periodic Classification Of Elements Earlier Attempts And Modern Peridic Table

CBSE Class 10 Science Chapter 5 Periodic Classification Of Elements Definitions


1. Need for classification:

One hundred and fourteen elements are forming millions of compounds. Though initially fewer elements were known (63 at the time of Mendeleev) there was a need to arrange the elements in a certain order to summarise their properties.

2. Dobereiner (1817) grouped the elements with similar properties in triads so that the atomic mass of the middle element was average of the other two

Example: triads: N, P, As, Ca, Sr. Ba and Cl. Br, I.

Read and Learn More CBSE Class 10 Science Short Answer Questions

3. Newlands (1866) gave the law of octaves. He found that every eighth element had properties similar to that of the first when arranged in increasing order of their atomic masses.

4 . Lother Meyer made a plot of atomic volumes of elements against their atomic masses. He found that similar elements occupied similar positions on the curve.

5. Mendeleev’s Periodic Table: He arranged the elements in increasing order of their atomic masses.

6. Modern Periodic Law: The physical and chemical properties of elements are the periodic function of their atomic number.

7. The Modern Periodic Table is based on modern periodic law which states that “properties of elements are a periodic function of their atomic numbers.” The periodicity in the properties of elements could be related to the periodicity in their electronic configurations. Modem Periodic Table is divided into 18 vertical columns called groups and 7 horizontal rows called periods.

8. Trends in the Modern Periodic Table

  1. In a group, the number of valence electrons remain the same. One in group, or three in group 3. On moving from left to right in a period, the number of valence electrons increases from one to eight.
  2. Atomic size increases down a group because of the addition of new shells. While in a period, the atomic size decreases from left to right. (Extra nuclear charge but no extra shell).
  3. Metallic and non-metallic character: Metallic character increases down a group (ease of loss of electron increases) and decreases along a period. Non-metallic character increases along a period from left to right.
  4. Ionization energy increases across a period (energy required to remove the most loosely bound electron from a gaseous neutral atom). This also follows that ionization energy decreases down a group.

9. Chemical reactivity:

On moving from left to right in a period, the chemical reactivity first decreases (Na→Mg→ Al→ Si) and then increases (P→ S→Cl  example for 3rd period.

10. Ionisation energy:

Ionisation energy is the energy required to remove an element. It is expressed in kJmol-1

Ag(g) +I.E → Ag+(g) +e

When more than one electron is to be removed, more energy is required because in this case electron is to be removed from the unipositive ion. Similarly, subsequent ionization energy will be still greater. i.e.,

1 st ionisationenergy <2 nd ionosationenergy <3 rd ionisation energy.

11. Electron affinity:

Whenever an atom gains an electron, energy is released. Thus electron affinity is the energy released when an electron is gained by a neutral gaseous atom to become a negatively charged ion.

For example:

12. Important characteristics of a period in the periodic table:

Valence electrons:

On moving from left to right in a period, the number of valence electrons increases from one to eight (except in the first period where the increase is from one to two only.)

 Valency:

The valency of elements increases from one to four, then decreases to one and becomes zero in the case of inert gases.

For example:

In compounds LiCl, BeCl2, BCl3 and CCl4 the valency of Li, Be, B and C are 1, 2, 3 and 4 respectively. Whereas in compounds, NH3, H2O, and HF, the valency of N, O, F are 3, 2 and 1 respectively.

Zero group: At the end of each period is the zero group element, the inert gas.

Size of atoms:

Atomic radii of the elements decrease gradually from left to right in a period because the nuclear charge increases but no extra shell is added.

Metallic character:

Metallic character decreases from left to right across a period and non-metallic character increases.

Ionisation energy:

Ionisation energy increases across a period from left to right. Ionisation energy is the energy required to remove the most loosely bound electron from a neutral gaseous atom.

Chemical reactivity:

On moving from left to right in a period, the chemical activity of elements first decreases and then increases. For example, in the third period, Na is very reactive, Mg, and Al are less reactive, Si is least reactive and the reactivity increases from P, S to Cl.

Oxides: The basic character of the oxides of the elements decreases and the acidic nature of the oxides of the elements increases.

For example:

In the 3rd period starting with sodium oxide, it is highly basic, and the next magnesium oxide is less basic. Then comes aluminium and silicon which give amphoteric oxides. They are the oxides of phosphorus and sulphur which are acidic. And the last chlorine oxide is highly acidic.

Electronegativity: Electronegativity increases on moving across a period from left to right. It is a measure of the tendency of the element to attract electrons towards itself.

13. Characteristics of a group:

Valency: In a group all the elements have the same valency.

For example:

group elements: Li, Na, K etc., all have a valency of +1. Elements ofgroup 17: Cl, Br, I etc. all have a valency of-1.

Size of atoms:

Atomic radii or the size of atoms of the elements increase on going down a group. This is due to the addition of new electronic shells.

Metallic character:

On descending a group the metallic character increases. For example, groups 14 and 15 begin with carbon and nitrogen which are non-metals. These groups end with lead and bismuth respectively which are metals. The oxides of the elements become increasingly basic.

Melting and boiling points:

The melting and boiling points of metals decrease on going down in a group.

Ionisation energy:

Ionisation energy decreases on moving down a group with the increase in atomic number. This is because the size of the atom increases and the valence electrons are farther removed from the attractive effect of the nucleus.

Chemical reactivity:

The chemical reactivity of metals increases on going down a group. For example, in group 1 of alkali metals, the chemical reactivity increases from lithium to francium. On the other hand, the chemical reactivity of metals decreases on going down in a group.

For example:

In group 17 of halogen elements (non-metals), fluorine is the most reactive and iodine is the least reactive

CBSE Class 10 Science Chapter 5 Periodic Classification Of Elements Short Question And Answers


Question 1. Did Dobereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and
find out.
Answer:

Yes, Dobereiner’s triads also existed in the columns of Newlands’ Octaves. For example, if you examine the first column ofNewlands’ Octave which has elements like

Lithium (Li), Sodium (Na) and Potassium (K). This also constituted Dobie Reiner’s triad: Li

⇒ \(\mathrm{Na}(23), \mathrm{K}(39)\left[\frac{7+39}{2}=23\right]\)

Question 2. What were the limitations ofDobereiner’s classification?
Answer:

Dobereiner’s classification could give only a limited no. of triads. Further, there were other elements which resembled a lot of triads but could not be accommodated. He could identify only three triads from the elements known at that time.

Question 3. What were the limitations of the Newlands of Octaves?
Answer:

Limitations of Newlands’ Law of Octaves:

The law of Octaves was applicable only upto Calcium (At. wt. = 40). After this every eighth element did not possess properties similar to that of the first as against his postulate. Though 56 elements were known at that time.

To fit elements into his table, at places he adjusted two elements into one slot. Cobalt (Co) and Nickel (Ni) were put in one slot and these were placed in the same column as Fluorine (F), Chlorine (Cl) and Bromine (Br) which have entirely different properties.

Iron (Fe) which resembles Cobalt and Nickel in properties, was placed far away

Question 4. Besides gallium, other elements have since been discovered that were left by Mendeleev in his periodic table. (Any two)
Answer:

Besides Gallium (Ga): The following two elements were discovered for the gaps left by

Mendeleev in his periodic table.

Scandium (Sc) and Germanium (Ge).

Question 5. Why are the noble gases placed in a separate group?
Answer:

Noble gases like Helium (He), Neon (Ne), and Argon (Ar) are chemically inert and are present in atmosphere in minimal concentrations. Thus, owing to their inert chemical behaviour and similar electronic configuration, they are justified to be placed in a separate group

Question 6. How could the Modern Periodic Table remove various anomalies of Mendeleev’s Periodic Table?
Answer:

By considering that the properties of elements are periodic functions of their atomic numbers, the following anomalies of Mendeleev’s periodic table were removed.

The anomaly of keeping isotopes in the same slot was solved as isotopes have similar properties and have the same atomic number but different atomic masses.

The atomic masses of the elements do not increase regularly in going from one element to the next but atomic numbers do. Now placement of hydrogen with alkali metals is justified based on their electronic configuration.

Question 7. Name two elements you would expect to show chemical reactions similar to magnesium. What is the basis for your choice?
Answer:

Beryllium (Be) and Calcium (Ca) will show similar chemical properties to that of Magnesium (Mg).

Basis of choice:

The basis of these two elements Be (at. no. 4) and Ca (at. no. 20) is that these belong to the same group and have the same number of outermost electrons of magnesium

Mg – 2,8,2

Be -2,2

Ca- 2,8,8,2

All three react with oxygen to give basic oxides such as MgO, BeO and CaO.

Question 8.

  1. Name Three elements that have a single electron in their outermost shells.
  2. Two elements that have two electrons in their outermost shells.
  3. Three elements with filled outermost shells.

Answer:

  1. Lithium (2, 1), Sodium (2, 8, 1) and Potassium (2, 8, 8, 1).
  2. Magnesium (2, 8, 2), Calcium (2, 8, 8, 2).
  3. Helium (2), Neon (2, 8), Argon (2, 8, 8).

Question 9. Which ofthe following statements is not a correct statement about the trends when going from left to right across the periods ofPeriodic Table?

  1. The elements become less metallic.
  2. The number of valence electrons increases.
  3. The atoms lose their electrons more easily.
  4. The oxides become more acidic.

Answer:

The atoms lose their electrons easily when going from left to right is not correct.

Question 10. 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 ofthe Periodic Table as

  1. Na
  2. Mg
  3. AI
  4. Si

Answer: 2. Mg. (X is bivalent)

Question 11. Which element has

  1. Two shells, both of which are filled with electrons?
  2. The electronic conjuration 2, 8, 2?
  3. A total of three shells, with four electrons in its valence shell?
  4. A total of two shells, with three electrons in its valence shell?
  5. Twice as many electrons in its second shell as in its first shell?

Answer:

Neon, Ne (2, 8)

Silicon, Si (2, 8, 4)

Question 12.

  1. What properties do all elements in the same column ofthe Periodic Table as boron have in common?
  2. What properties do all elements in the same column of the Periodic Table as fluorine have in common?

Answer:

  1. The elements in the same column as Boron have three electrons in their outermost shell just like Boron. All are metalloids.
  2. Elements in the same column as Fluorine have seven electrons in their outermost shell and form acidic oxides like Fluorine does.

Question 13. 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?
Answer:

Electronic configuration of (7): 2, 5.

Electronic configuration of (15): 2, 8, 5.

Nitrogen will be more electronegative than phosphorous because the outermost shell in nitrogen is nearer to the nucleus and thus positive nucleus will attract electrons strongly.

Question 14. How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?
Answer:

The position ofan atom/element in the periodic table is related to the number ofelectrons 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 II, all elements have two electrons in their outermost shell. In group 15, all elements have 5 electrons in their outermost shells.

Question 15. Choose from the following: 20Ca, 3Li, 11Na, 10Ne

  1. An element having 2 shells completely filled with electrons.
  2. Two elements belonging to the same group ofperiodic table.

Answer:

10Ne has electronic configuration 2, 8. Both shells are completely filled.

3Li and 11Na belong to the same group i.e. 1st group.

Question 16. Write two achievements of Mendeleev’s periodic table.
Answer:

  1. It could classify all the elements discovered at that time.
  2. It helped in the discovery of new elements.

Question 17.

  1. Name the element with atomic number 17.
  2. To which period does it belong?
  3. To which group does it belong?
  4. Write its electronic configuration.

Answer:

  1. Chlorine
  2. 3rd
  3. 17th
  4. K – 2 , L -8 , M – 7

Question 18. An element X(atomic number 17) reacts with an element Y(atomic number 20) to form a divalent halide.

  1. What is the position of elements X and Yin in the periodic table?
  2. What will be the nature of the oxide of element Y? Identify the nature of bonding in the compound formed.

Answer:

X- non-metal

Y- metal

YX2

1. X- Position- Group- 17, period- 3

Y- Position- Group- 2, Period- 4

2. Basic YO, ionic bond.

Question 19. Two elements M and N belong to group 1 and 2 respectively and are in the same period of the periodic table. How do the following properties of M and N vary:

  1. Sizes oftheir atoms
  2. Their metallic characters
  3. Their valencies in forming oxides
  4. Formulae oftheir chlorides

Answer: The size of atom decreases from left to right. Atom ofM is bigger than atom ofN.

M is more metallic than N.

Group 1: Valency 1

Group 2: Valency 2

Formulae of chloride: MCI, NCl2

Question 20. On the basis of electronic configuration, how will you identify the first and the last element of a period.
Answer:

Ist element has 1 valence electron and last element has 8 valence electrons. A number of shells remain the same in the same period.

Question 21. Explain the basic character of oxide ofelements 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 the acidic and basic nature of oxides canbe related to the electronegativity of the element.

As the electronegativity of the element increases along a period the acidic character of the oxide increases and as the electronegativity of the element decreases down the group the basic character of the oxide increases.

Question 22. Describe the basic character ofthe oxides of third period elements across the period from left to right.
Answer:

The basic nature decreases across the period.

Na and Mg are basic.

Al and Si are amphoteric.

P, Cl, and S are acidic.

Question 23. List the anomalies of Mendeleev’speriodic table which were renamed by modern periodic law.
Answer:

Anomalies of Mendeleev’s periodic table:

  1. The correct position of hydrogen was not assigned.
  2. The position of isotopes was not defined.
  3. Placement of heavier element before lighter element.

Question 24.

  1. Amongst the following elements identify the ones that would form anions: K, O, Na, F, Ca.Cl, Mg
  2. Write the electronic configuration of anions identified above.

Answer:

O, F and Cl would form anions.

O2- = 2, 8

F = 2, 8

Cl= 2, 8,8

Question 25. “Elements in Periodic Table showperiodicity of properties.”List any four such properties.
Answer:

  1. Atomic size
  2. Valency or combining capacity
  3. Metallic property
  4. Non-metallic property

Question 26. Mention any two trends exhibited by elements when we go from left to right across the period of the periodic table.
Answer:

  1. Atomic radius decreases.
  2. Metallic character decrease.

Question 27. State the reason for the following:

  1. The elements of the same group have similar chemical properties.
  2. The elements ofthe same period have different properties.

Answer:

  1. Because of a same number of valence electrons.
  2. Because of different numbers of valence electrons

Question 28. Calcium is an element with the atomic number 20.

  1. Is it a metal or a non-metal?
  2. Is it more reactive than Mg or less?
  3. What will be its valency?
  4. What will be the formula of its chloride?

Answer:

  1. It is a metal.
  2. It is more reactive than Mg.
  3. Its valency is 2.
  4. CaCl2.

Question 29. What are metalloids? How many electrons can he present in the valence shell of their atoms? In which part of the periodic table these are located? What type of oxides are formed by these elements?
Answer:

Metalloids are elements which resemble both metals and non-metals. The valence shell of metalloids contains 3, 4, 5, and 6 elements starting from periods 2 to 5 respectively. These are found on the right side of the table in the zig-zag column,

Example: Boron, silicon, germanium, arsenic etc. These form amphoteric oxides.

Question 30. What is electronegativity? How does it compare with electron affinity?
Answer:

Though both Electronegativity and Electron Affinity refer to the attraction of electrons but are used in different contexts. Electronegativity refers to the attraction of bonding electrons or shared pairs of electrons whereas Electron Affinity refers to the attraction of electrons by an isolated gaseous atom.

Question 31. Given below are some elements ofthe modern periodic table. The atomic number of the elements are given in parentheses: A (4), B (9), C (14), D (19), E (20)

  1. Select the element that has one electron in the outermost shell. Also, write the electronic configuration of this element.
  2. Which two elements amongst these belong to the same group? Give a reason for your answer.
  3. Which two elements amongst these belong to the same period? Which one of the two has a bigger atomic radius?

Answer:

1. D ; 2, 8, 8, 1

2. A and E belong to the same group as both have the same number of valence electrons i.e., same number of electrons (2) in the outermost shell.

3. A and B/D and E. A has a bigger atomic radius than B or D has a bigger atomic radius than E.

Question 32. The three elements A, B, and C with similar properties have atomic masses X, Y, and Z respectively. The mass of Y is approximately equal to the average mass of X and Z. What is such an arrangement of elements called as? Give one example of such a set of elements.
Answer:

Dobereiner triad;

Example:  Lithium, Sodium, Potassium

Question 33. Elements have been arranged in the following sequence based on their increasing atomic masses. F, Na, Mg, Al, Si, P, S, Cl, Ar, K

  1. Pick two sets of elements which have similar properties.
  2. The given sequence represents which law of classification of elements?

Answer:

1.

  1. F and Cl
  2. Na and K

2. Newlands’ law of octaves.

Question 34. Can the following groups of elements be classified as Dobereiner’s triad?

  1. Na, Si. Cl
  2. Be. Mg, Ca

Atomic mass of Be 9; Na 23; Mg 24; Si 28; Cl 35; Ca 40

Explain by giving a reason.

Answer:

No, because all these elements do not have similar properties although the atomic mass of silicon is average of atomic masses of sodium (Na) and chlorine (Cl).

Yes, because they have similar properties and the mass of magnesium (Mg) is roughly the average of the atomic mass ofBe and Ca.

Question 35. In Mendeleev’s Periodic Table, the elements were arranged in the increasing order of their atomic masses. However, cobalt with atomic mass of  58.93 amu was placed before nickel having an atomic mass of 58.71 amu. Give a reason for the same.
Answer:

  1. The properties of cobalt are similar to those of Rhodium and Iridium (Ir) (the same group) and.
  2. The properties of nickel are similar to those of Palladium (Pd) and Platinum (Pt) (same group).

Question 36. “Hydrogen occupies a unique position in Modern Periodic Table”. Justify the statement.
Answer:

Though hydrogen is a non-metal, it has been placed at the top of group-1 above the alkali metals because its electronic configuration is similar to alkali metals i.e., (have valence electronin the outermost shell). But while discussing the alkali metals, hydrogen is not considered. Thus, hydrogen occupies a unique position is modern periodic table.

Question 36. Three elements A, B, and C have 3, 4 and 2 electrons respectively in their outermost shell. Give the group number to which they belong in the Modern  Periodic Table. Also, give their valencies
Answer:

CBSE Class 10 Science Chapter 5 Periodic Classification Of Elements Modern Periodic Table

Question 38. Compare the radii of two species X and Y. Give reasons for your answer.

  1. X has 12 protons and 12 electrons
  2. Y has 12 protons and 10 electrons

Answer:

  1. Radii of Y < Radii of X
  2. Because Y is the cation of X.

Question 39. Arrange the following elements in increasing order oftheir atomic radii’

  1. Li, Be, F, N
  2. Cl, At, Br,I

Answer:

  1. F < N < Be < Li
  2. Cl < Br <I < Al

Question 40. Identify and name the metals out ofthe following elements whose electronic configurations are given below:

  1. 2, 8, 2
  2. 2, 8, 1
  3. 2, 8, 7
  4. 2, 1

Answer:

(1), (2) and (4)

1- Magnesium

2 – Sodium

4 – Lithium

Question 41. Write the formula of the product formed when the element A (atomic number 19) combines with the element B (atomic number 17).

Draw its electronic dot structure. What is the nature ofthe bond formed?

CBSE Class 10 Science Chapter 5 Periodic Classification Of Elements Ionic Bond

A = K (Potassium)

B = Cl (Chlorine)

Question 42. Arrange the following elements in the increasing order oftheir metallic characters Mg, Ca, K, Ge, Ga
Answer:

Ge < Ga < Mg < Ca < K

Question 43. Identify the elements with the following properties and arrange them in increasing order of their reactivity

  1. An element which is a soft and reactive metal
  2. The metal which is an important constituent of limestone
  3. The metal which exists in a liquid state at room temperature

Answer:

  1. Na or K
  2. Hg
  3. Increasing order oftheir reactivity as Hg < Ca < Mg < Ca < K

Question 44. What are metalloids? How many electrons can be present in the valence shell of their atoms? In what part of the periodic table these are located? What type of oxides are formed by these elements?
Answer:

Metalloids are elements which resemble both metals and non-metals. The valence shell of metalloids contains 3, 4, 5, 6 elements starting from periods 2 to 5 respectively. These are found on the right side of the table in the zig-zag column,

Examples: Boron, silicon, germanium, arsenic, etc. These form amphoteric oxides.

CBSE Class 10 Science Chapter 5 Periodic Classification Of Elements Multiple Choice Questions


Question 1. Upto which element, the Law ofOctaves was found to be applicable

  1. Oxygen
  2. Calcium
  3. Cobalt
  4. Potassium

Answer: 2. Calcium

Question 2. According to Mendeleev’s Periodic Law, the elements were arranged in the periodic table in the order of

  1. Increasing atomic number
  2. Decreasing atomic number
  3. Increasing atomic masses
  4. Decreasing atomic masses

Answer: 3. Increasing atomic masses

Question 3. In Mendeleev’s Periodic Table, gaps were left for the elements to be discovered later. Which ofthe following elements found a place in the periodic table later?

  1. Chlorine
  2. Silicon
  3. Germanium
  4. Oxygen

Answer: 1. Chlorine

Question 4. Which of the following statement (s) about the Modern Periodic Table are incorrect?

1. The elements in the Modern Periodic Table are arranged on the basis oftheir decreasing atomic number

2. The elements in the Modern Periodic Table are arranged on the basis oftheir increasing atomic masses

3. Isotopes are placed in adjoining group(s) in the Periodic Table

4. The elements in the Modern Periodic Table are arranged based on their increasing atomic number

  1. 1 Only
  2. 1, 2 and 3
  3. 1, 2 and 4
  4. 4 only

Answer: 2. 1, 2 and 3

Question 5. Which ofthe following statements about the Modern Periodic Table is correct?

  1. It has 18 horizontal rows known as Periods
  2. It has 7 vertical columns known as Periods
  3. It has 18 vertical columns known as Groups
  4. It has 7 horizontal rows known as Groups

Answer: 3. It has 18 vertical columns known as Groups

Question 6. Which ofthe given elements A, B, C, D, and E with atomic numbers 2, 3, 7, 10 and 30 respectively belong to the same period?

  1. A, B, C
  2. B, C, D
  3. A,D,E
  4. B, D, E

Answer: 2. B, C, D

Question 7. The elements A, B, C, D, and E have atomic number 9, 11, 17, 12 and 13 respectively. Which pair of elements belong to the same group?

  1. A and B
  2. A and C
  3. B and D
  4. D and E

Answer: 3. B and D

Question 8. Where would you locate the element with electronic configuration 2, 8 in the Modern Periodic Table?

  1. Group 8
  2. Group 2
  3. Group 18
  4. Group 10

Answer: 3. Group 18

Question 9. An element which is an essential constituent of all organic compounds belongs to

  1. Group 1
  2. Group 14
  3. Group 15
  4. Group 16

Answer: 2. Group 14

Question 10. Which ofthe following is the outermost shell for elements of period 2?

  1. K shell
  2. M shell
  3. L shell
  4. N shell

Answer: 2. M shell

Question 11. Which one ofthe following elements exhibits a maximum number of valence electrons?

  1. Na
  2. Al
  3. Si
  4. P

Answer: 4. P

Question 12. Which ofthe following gives the correct increasing order ofthe atomic radii of

  1. O, F,N
  2. N, F, O
  3. O, N, F
  4. F,O, N

Answer: 4. F, O,N

Question 13. Which among the following elements has the largest atomic radii?

  1. Na
  2. Mg
  3. COK
  4. Ca

Answer: 3. COK

Question 14. Which ofthe following elements would lose an electron easily?

  1. Mg
  2. Na
  3. K
  4. Ca

Answer: 3. K

Question 15. Which ofthe following elements does not lose an electron easily?

  1. Na
  2. F
  3. Mg
  4. Al

Answer: 2. F

Question 16. Which ofthe following are the characteristics of isotopes ofan element?

1. Isotopes ofan elements have same atomic masses

2. Isotopes ofan elements have same atomic number

3. Isotopes ofan elements show same physical properties

4. Isotopes ofan elements show same chemicalproperties

  1. 1, 3 and 4
  2. 2,3 and 4
  3. 2 and 3
  4. 2 and 4

Answer: 4. 2 and 4

Question 17. Arrange the following elements in the order oftheir decreasing metallic characters Na, Si, Cl, Mg, Al

  1. Cl > Si >Al > Mg >Na
  2. Na >Mg > Al > Si > Cl
  3. Al >Na >Si>Ca> Mg
  4. Na >Al> Mg > Cl >Si

Answer: 2. Na >Mg > Al > Si > Cl

Question 18. Arrange the following elements in the order oftheir increasing non-metallic characters Li, O, C, Be, F

  1. F < O < C < Be <Li
  2. Li < Be < C < O <F
  3. F < O < C < Be <Li
  4. F < O < Be < C <Li

Answer: 2. Li < Be < C < O <F

Question 19. What type of oxide would Eka-aluminium form?

  1. EO3
  2. E3O2
  3. E2O3
  4. EO

Answer: 3. E2O3

Question 20. Three elements B, Si and Ge are

  1. Metals
  2. Non-metals
  3. Metalloids
  4. Metal, non-metal and metalloid respectively

Answer: 3. Metalloids

Question 21. Which ofthe following elements will form an acidic oxide?

  1. An element with atomic number 7
  2. An element with atomic number 3
  3. An element with atomic number 12
  4. An element with atomic number 19

Answer: 1. An element with atomic number 7

Question 22. The element with atomic number 14 is hard and forms acidic oxide and a covalent halide.

  1. To which ofthe following categories does the element belong?
  2. Metal
  3. Metalloid
  4. Left-hand side elements

Answer: 3. Metalloid

Question 23. Which one of the following depicts the correct representation of the atomic radius of an atom?

CBSE Class 10 Science Chapter 5 Periodic Classification Of Elements Atomic Radius

  1. 1 and 2
  2. 2 and 3
  3. 3 and 4
  4. 1and 4

Answer: 2. 2 and 3

Question 24. Which one ofthe following does not increase while moving down the group of the periodic table?

  1. Atomic radius
  2. Valency
  3. Metallic character
  4. Number of shells in an element

Answer: 3. Metallic character

Question 25. On moving from left to right in a period in the periodic table, the size ofthe atom

  1. Increases
  2. Decreases
  3. Does not change appreciably
  4. First decreases and then increases

Answer: 2. Decreases

Question 26. Which of the following sets of elements is written in order of their increasing metallic character?

  1. Be, Mg, Ca
  2. Na, Li, K
  3. Mg,Al,S
  4. C, O, N

Answer: 1.Be, Mg, Ca

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