Lakhmir Singh solutions for Chemistry (Science) [English] Class 10 chapter 5 - Periodic Classification Of Elements [Latest edition]

 On what basis did mandeleev arrange the elements in his periodic table?

On what basis elements are arranged in periodi table now?

State whether the following statement is true of false:

Newlands divided the elements into horizontal rows of eight elements each.

State whether the following statement is true of false:

According to Mendeleev's periodic law, the properties of elements are a periodic function of their atomic numbers.

State whether the following statement is true of false:

The elements in a group have consecutive atomic numbers.

Name the Russian chemist who said that the properties of elements are a periodic function of their atomic masses.

Rewrite the following statement after correction, if necessary:

Groups have elements with consecutive atomic numbers.

Rewrite the following statement after correction, if necessary:

Periods are the horizontal rows of elements.

Rewrite the following statement after correction, if necessary:

 Isotopes are the elements of the same group.

Name the scientist who gave the Law of octaves in the early classification of elements.

Name the scientist who gave Law of triads in the early classification of elements.

A, B and C are the elements of a Dobereiner's triad. If the atomic mass of A is 7 and the of C is 39, what should be the atomic mass of B?

X and Y are the two elements having similar properties which obey Newland's laws of octaves. How many elements are there in-between X and Y?

What was the Mendeleev's basis for the classification of elements?

In the classification of the them known elements, Mendeleev was guided by two factors. What are those two factors?

Name two elements whose properties were predicted on the basis fo their positions in Mendeleev's periodic table.

The three elements predicted by Mendeleev from the gaps in his periodic table were known as eka-boron, eka-aluminimum and eka-silicon. What names were given to these elements when they were discovered later on?

Name two elements whose properties were predicted on the basis fo their positions in Mendeleev's periodic table.

State one example of a Dobereiner's triad, showing in it that the atomic mass of middle element is half-way between those of the other two.

Which group of elements could be placed in Mendeleev's periodic table later on, without disturbing the order? Give reason.

Fill in the following blank with suitable word:
 The basis for modern periodic table is ...............

Fill in the following blank with suitable word:
 The horizontal rows  in a periodic table are called ...............

Fill in the following blank with suitable word:

Group 1 elements are called ...............

Fill in the following blank with suitable word:
Group 17 elements are known as ...............

Fill in the following blank with suitable word:

Group 18 elements are called ...............

Fill in the following blank with suitable word:

According to Newland's classification of elements, the properties of sulphur are similar to those of oxygen because sulphur is the ............... element starting from oxygen.

 What is meant by a group, in a periodic table?

What is meant by a period, in a periodic table?

How many periods and groups are there in the long form of periodic table?

Give two example of group 1 elements.

Give two example of group 17 elements.

Give two example of group 18 elements.

In the Modern Periodic Table, which are the metals among the first ten elements?

What is the significance of atomic number in the modern classification of elements? Explain with the help of an example.

How were the positions of isotopes of an element decided in the modern periodic table?

How were the positions of cobalt and nickel resolved in the modern periodic table?

where should hydrogen be placed in the modern periodic table? Give reason for your answer.

On which side of the periodic table will you find metals?

On which side of the periodic table will you find non-metals?

What is the name of those elements which divide metals and non-metals in the periodic table?

Name three elements that have a single electron in their outermost shells.

 Name two elements that have two electrons in their outermost shells.

Name three elements with filled outermost shells.

What is Debereiner's law of triads? Explain with the help of one example of a Dobereiner's triad.

What is Newlands' law of octaves? Explain with an example.

Did Dobereiner's triads also exist in the columns of Newlands' law of octaves? Explain your answer.

What were the limitations of Dobereiner's classification of elements?

What were the limitations of Newlands’ Law of Octaves?

State the periodic law on which Mendeleev's periodic table table was based. Why and how was this periodic law changed?

Explain why, the noble gases are placed in a separate group.

State the merits of Mendeleev's classification of elements.

Describe two anomalies of Mendeleev's periodic classification of elements.

How do the properties of eka-aluminium element predicted by Mendeleev compare with the actual properties of gallium element?

What name were given by Mendeleev to the then undiscovered element scandium.

What name were given by Mendeleev to the then undiscovered element gallium?

What name were given by Mendeleev to the then undiscovered element germanium?

Why do we classify elements?

What were the two criteria used by Mendeleev to classify the elements in his periodic table?

Why did Mendeleev leave some gaps in his periodic table?

In Mendeleev's periodic table, why was there no mention of noble gases like helium, neon and argon?

Would you place the two isotopes of chlorine, CI-35 and CI-37 in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? Justify your answer.

State Mendeleev's periodic law.

What chemical properties of elements were used by Mendeleev in creating his periodic table?

State any three limitations of Mnedeleev's classification of elements.

Besides gallium, which two other elements have since been discovered for which Mendeleev had left gaps in his periodic table?

State modern periodic law.

How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?

How could the Modern Periodic Table remove various anomalies of Mendeleev’s Periodic Table?

Is it possible to have an element having atomic number 1.5 placed between hydrogen and helium?

Name the scientist who prepared modern periodic table.

In Mendeleev's periodic table, gap was not left for one of the following elements. This element is:

(a) gallium
(b) beryllium
(c) germanium
(d) scandium

The Newland's law of octaves for the classification of elements was not found to be applicable only up to the element:

(a) potassium
(b) calcium
(c) cobalt
(d) phosphorus

According to Mendeleev's periodic law, the elements were arranged in the periodic table in the order of: ______ 

The three elements having chemical symbols of Si, B and Ge are:

(a) all metals
(b) all non-metals
(c) all metalloids
(d) Si is metalloid, B is metal and Ge is non-metal

In Mendeleev's periodic table, gaps were left for the elements to be discovered later on. An element which found a vacant place in the periodic table later on is:

(a) Be
(b) Si
(c) Ge
(d) Se

The three imaginary elements X, Y and Z represent a Dobernener's triad. If the atomic mass of element X is 14 and that of element Y is 46, then the atomic mass of element Z will be:

(a) 28
(b) 60
(c) 78
(d) 72

The atomic numbers of four elements P, Q, R and S are 6, 8, 14 and 16 respectively. Out of these, the element known as metalloid is:

(a) P
(b) Q
(c) R
(d) S

Which of the following statement is correct in regard to the classification of elements?

(a) Elements in modern periodic table are arranged on the basis of increasing atomic masses.
(b) Elements in Mendeleev's periodic table are arranged on the basis of increasing atomic numbers.
(c) In modern periodic table, the element nickel of lower atomic mass is kept before the element cobalt of higher atomic mass.
(d) In modern periodic table, the isotopes of chlorine having different atomic masses are kept in the same group.

Which of the following statement 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.

An element X forms an oxide X₂O₃. In which group of Mendeleev's periodic table is this element placed?

(a) group II
(b) group III
(c) group V
(d) group VIII

The modern periodic table was prepared by ______.

The atomic particle whose number in the atoms of an element always remains the same and which forms the real basis for the modern classification of elements is:

(a) electron
(b) proton 
(c) neutron
(d) meson

The atomic masses of three elements X, Y and Z having similar chemical properties are 7, 23 and 39 respectively.

(a) Calculate the average atomic mass of elements X and Z.
(b) How does the average atomic mass of elements X and Z compare with the atomic mass of element Y?
(c) Which law of classification of elements is illustrated by this example?
(d) What could the elements X, Y and Z be?
(e) Give another example of a set of elements which can be classified according to this law.

In the following set of element, one element does not belong to the set. Select this element and state why it does not belong:
Calcium, Magnesium, Sodium, Beryllium

In the following set of elements, one element does not belong to the set. Select this element and state why it does not belong:
Oxygen, Nitrogen, Carbon, Chlorine, Fluorine

Can the following groups of elements be classified as Dobereiner's triads?

(a) Na, Si, Cl
(b) Be, Mg, Ca
Give reason for your answer.
(Atomic masses : Be 9 ; Na 23 ; Mg 24 ; Si 28 ; Cl 35.5 ; Ca 40)

Consider the following elements:
Na, Ca, Al, K, Mg, Li

Which of these elements belong to the same period of the periodic table?

Consider the following elements:
Na, Ca, Al, K, Mg, Li

Which of these elements belong to the same group of the periodic table?

Which element has two shells, both of which are completely filled with electrons?

Which element has the electronic configuration 2, 8, 2?

Which element has a total of three shells, with four electrons in its valence shell?

Which element has a total of two shells, with three electrons in its valence shell?

Which element has twice as many electrons in its second shell as in its first shell?

Consider the following elements:
Ca, Cl, Na, I, Li, Ba, Sr, K, Br

Separate these elements into three groups (families) of similar properties. State one property in each case on the basis of which you have made your choice.

Mendeleev predicted the existence of certain elements not known at that time and named two of them as eka-aluminium, and eka-silicon.

(a) Name the element which has taken the place of (i) eka-aluminium, and (ii) eka-silicon
(b) Mention the period/periods of these elements in the modern periodic table.
(c) Write the group/ groups of these elements in the modern periodic table.
(d) Classify these elements as metals, non-metals or metalloids.
(e) How many valence electrons are present in the atoms of each of these elements?

A part of the early classification of elements has been given below:

(a) Which law of classification of element is illustrated by the above arrangement of elements?
(b) Name the scientist who proposed such a classification of elements.
(c) Why is such a classification of elements compared with a characteristics of musical scale?
(d) State one limitation of this classification of elements.

Give alongside is a part of the periodic table :
As we move horizontally from left to right:

(i) What happens to the metallic character of the elements?
(ii) What happens to the atomic size?

How would the tendency to gain electrons change on moving from left to right in a period of the periodic table?

How would the tendency to lose electrons change as we go from left to right across a period of the periodic table?

 How does the chemical reactivity of alkali metals vary on going in group 1 of the periodic table?

How does the chemical reactivity of the halogens vary on going in group 17 of the periodic table?

What property do all elements in the same column of the Periodic Table as boron have in common?

What property do all elements in the same column of the Periodic Table as fluorine have in common?

What is the number of valence electrons in the atoms of first elements in a period?

What is the usual number of valence electrons in the atoms of the last element in a period?

State whether the following statement is true or false:
On going down in a group of the periodic table, the number of valence electrons increases.

What is the major characteristic of the first elements in the periods of the periodic table? What is the general name of such elements?

How do the atomic radii of elements change as we go from left to right in a period of the periodic table?

What happens to the metallic character of the elements as we go down in a group of the periodic table?

How does the number of valence electrons vary on moving from left or right in the first period of the periodic table?

How does the number of valence electrons vary on moving from left or right in the second period of the periodic table?

How does the valency of elements change of moving from left to right in the third period of the periodic table?

How does the valency of elements vary in going down a group of the periodic table?

Name the element which is in  first group and third period.

Name the element which is in seventeenth group and second period.

How do electronic configurations of elements change in second period of periodic table with increase in atomic numbers?

Arrange the following elements in increasing order of their atomic radii:
Li, Be, F, N

Arrange the following elements in the increasing order of their metallic character:
Mg, Ca, K, Ga

Rewrite the following statement after correction, if necessary:

Elements in the same period have equal valency

Rewrite the following statement after correction, if necessary:

The metallic character of elements in a period increases gradually on moving from left to right.

Fill in the following blank with suitable word:
 The horizontal rows  in a periodic table are called ...............

Fill in the blank in the following statement:

In going across a period (right to left) in periodic table, the atomic size of the atom ...............

Fill in the blank in the following statement:

On moving form right to left in the second period, the number of valency electrons ...............

Fill in the blank in the following statement:

On going down in a group in the periodic table, the metallic character of elements ...............

Fill in the blank in the following statement:

The tendency to gain an electron ............... on moving down in a group of the periodic table.

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?

An element X belongs to group 2 and another element Y belongs to group 15 of the periodic table:

(a) What is the number of valence electron in X?
(b) What is the valency of X?
(c) What is the number of valence electrons in Y?
(d) What is the valency of Y?
Explain how you have arrived at your answers.

What is a period in a periodic table?

How do atomic structures (electron arrangements) change in a period with increase in atomic numbers from left to right?

 How does Chemical reactivity of elements change on going from left to right in a period of the periodic table?

Give example in support of your answer.

How does Nature of oxides of elements change on going from left to right in a period of the periodic table?

Give examples in support of your answer.

How does the size of atoms (atomic size) generally vary in going from left to right in a period of the periodic table? Why does it vary this way?

What happens to the metallic character of the elements as we move from left to right in a period of the periodic table?

 Explain why All the elements of a group have similar chemical properties.

 Explain why All the elements of a period have different chemical properties.

How does the electropositive character of elements change on going down in a group of the periodic table?

 State how the valency of elements varies in a group of the periodic table?

State how the valency of elements varies in a period of the periodic table?

What is the fundamental difference in the electron configurations between the group 1 and group 2 elements?

On the basis of electronic configuration, how will you identify chemically similar elements?

 On the basis of electronic configuration, how will you identify the first element of a period?

What is the usual number of valence electrons and valency of group 18 elements of the periodic table?

 What happens to the number of valence electrons in the atoms of elements as we go down in a group of the periodic table?

What is the main characteristic of the last elements in the periods of the periodic table? What is the general name of such elements?

 What is the number of elements is 1st period the modern periodic table?

How does the atomic size vary on going down from top to bottom in a group of the periodic table? Why does it vary this way?

Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?

 How does the tendency to lose electrons change as we go down in group 1 of the periodic table? Why does it change this way?

Why does the size of the atoms progressively become smaller when we move from sodium (Na) to chlorine (Cl) in the third period of the periodic table?

 In the modern Periodic Table, why does cobalt with higher atomic mass of 58.93 appear before nickel having lower atomic mass of 58.71?

What are the periods in a periodic table? Give two characteristics of each.

What are the groups in a periodic table? Give two characteristics of each.

 In terms of electronic configurations, explain the variation in the size of the atoms of the elements belonging to the same period and same group ?

 Given alongside is a part of the periodic table. As we move vertically downward from Li to fr?

 What happens to the size of atoms?

 Given alongside is a part of the periodic table. As we move vertically downward from Li to Fr:

 What happens to their metallic character?

Name two properties of elements whose magnitudes change when going from top to bottom in a group of the periodic table. In what manner do they change?

Rewrite the following statement after correction, if necessary:

Groups have elements with consecutive atomic numbers.

Explain why, the first period of the periodic table has only two elements whereas second period has eight elements

Why do elements in the same group show similar properties but the elements in different groups show different properties?

For each of the following triads, name the element with the characteristics specified below:

State one reason for keeping fluorine and chlorine in the same of the periodic table.

What are the merits of the modern periodic table of elements?

What is a group in the periodic table?

 In which part of a group would you separately expect the elements to have the greatest metallic character

In which part of a group would you separately expect the elements to have the largest atomic size?

In what respects do the properties of group 1 elements differ from those of group 17 elements? Explain with examples by taking one element from each group.

From the standpoint of atomic structure, what determines which element will be the first and which the last in a period the periodic table?

 Explain why, the properties of elements are repeated after 2, 8, 18 and 32 elements in the periodic table.

What are the advantages of the periodic table?

 Which of the following statements is not a correct statement about the trends when going from left to right across the periods of periodic Table.

The electronic configuration of the atom of an element X is 2, 8, 4. In modern periodic table, the element X is places in :

(a) 2nd group
(b) 4th group
(c) 14th group
(d) 8th group

The atomic number of an element is 20. In modern periodic table, this element is placed:

(a) 2nd period
(b) 4th period
(c) 3rd period
(d) 1st period

Five elements A, B, C, D and E have atomic numbers of 2, 3, 7, 10 and 18 respectively. The elements which belong to the same period of the periodic table are:

(a) A, B, C
(b) B, C, D
(c) A, D, E
(d) B, D, E

The elements A, B, C, D and E have atomic numbers 9, 11, 17, 12 and 13 respectively. The pair of elements which belongs to the same group of the periodic table is:

(a) A and B
(b) B and D
(c) A and C
(d) D and E

Which of the following element would lose an electron easily?

(a) Mg
(b) Na
(c) K
(d) Ca

Which of the following element does not lose an electron easily?

(a) Na
(b) F
(c) Mg
(d) Al

Where would you locate the element with electronic configuration 2, 8 in the modern periodic table?

An element which is an essential constituent of all organic compounds belongs to following group of modern periodic table:

(a) group 4
(b) group 14
(c) group 15
(d) group 16

Which of the following is the valence shell for the elements of second period of the modern periodic table?

(a) M shell
(b) K shell
(c) L shell
(d) N shell

The element which has the maximum number of valence electrons is:
(a) Na
(b) P
(c) Si
(d) A

The correct increasing order of the atomic radii of the elements oxygen, fluorine and nitrogen is:
(a) O, F, N
(b) N, F, O
(c) O, N, F
(d) F, O, N

The atomic numbers of the elements Na, Mg, K and Ca are 11, 12, 19 and 20 respectively. The element having the largest atomic radius is:

(a) Mg
(b) Na
(c) K
(d) Ca

The correct formula of the oxide of Eka-aluminium element predicted by Mendeleev was:

(a) EaO₃
(b) Ea₃O₂
(c) Ea₂O₃
(d) EaO

The element which can from an acidic oxide should be the one whose atomic number is:

(a) 6
(b) 16
(c) 12
(d) 19

The element which forms a basis oxide has the atomic number of:

(a) 18
(b) 17
(c) 14
(d) 19

Which one of the following does not increase while moving down the group of the periodic table?

Which of the following set of elements is written correctly in the order of their increasing metallic character?

(a) Mg, Al, Si
(b) C, O, N
(c) Na, Li, K
(d) Be, Mg, Ca

An atom has the electron structure of 2, 7.
(a) What is the atomic number of this atom?
(b) To which of the following would it be chemically similar?
₇N, ₁₅P, ₁₇Cl, ₁₈Ar
(c) Why would you expect it to be similar?

Consider the following elements:
₂₀Ca, ₈O, ₁₈Ar, ₁₆S, ₄Be, ₂He
Which of the above elements would you expect to be:

(i) very stable?
(ii) in group 2 of the periodic table?
(iii) in group 16 of the periodic table?

In each of the following pair, choose the atom having the bigger size:

(a) Mg (At. No.12) or Cl (At. No.17)

^{In each of the following pair, choose the atom having the bigger size:}

^{Na (At. No. 11) or K (At. No. 19)}

The atomic numbers of three elements A, B and C are given below:

(i) Which element belongs to group 18?
(ii) Which element belongs to group 15?
(iii) Which element belongs to group 13?
(iv) To which period/periods do these elements belong?

An element X belongs to 3rd period and group 2 of the periodic table. State:

(a) number of valence electrons
(b) valency
(c) metal or non-metal
(d) name of the element

The following diagram shows a part of the periodic table in which the elements are arranged according to their atomic numbers. (The letters given here not the chemical symbols of the elements):

(i) Which element has a bigger atom, a or f?
(ii) Which element has a higher valency, k or o?
(iii) Which element is more metallic i or k?
(iv) Which element is more non-metallic, d or g?
(v) Select a latter which represents a metal of valency 2.
(vi) Select a letter which represents a non-metal of valency 2.

An element X is in group 2 of the periodic table What will be the formula of its chloride?

An element X is in group 2 of the periodic table what will be the formula of its oxide?

An element Y is in second period and group 16 of the periodic table:

(i) Is it a metal or non-metal?
(ii) What is the number of valence electrons in its atom?
(iii) What is its valency?
(iv) What is the name of the element?
(v) What will be the formula of the compound formed by Y with sodium?

As element X has mass number 40 and contains 21 neutrons in its atom. To which group of the periodic table does it belong?

The element X forms a compound X₂Y. Suggest an element that Y might be and give reasons for your choice.

An element X combines with oxygen to form an oxide XO. This oxide is electrically conducting.

(a) How many electrons would be there in the outermost shell of the element X?
(b) To which group of the periodic tables does the element X belong?
(c) Write the formula of the compound formed when X reacts with chlorine.

An element A has an atomic number of 6. Another element B has 17 electrons in its one neutral atom.

(a) In which groups of the periodic table would you expect to find these elements?
(b) what type of bond is formed between A and B?
(c) Suggest a formula of the compound formed between A and B.

The elements A, B, C and D belong to groups 1, 2, 14 and 17 respectively of the periodic table. Which of the following pairs of elements would produce a covalent bond?
(i) A and D
(ii) C and D
(iii) A and B
(iv) B and C
(v) A and C

An element X from group 2 reacts with element Y from group 16 of the periodic table.
(a) What is the formula of the compound formed?
(b) What is the nature of bond in the compound formed?

A metal X is in the first group of the periodic table. What will be the formula of its oxide?

An element A from group 14 of the periodic table combines with an element B from group 16.

(i) What type of chemical bond is formed?
(ii) Give the formula of the compound formed.

An element X from group 2 of the periodic table reacts with an element Y from group 17 to form a compound.

(a) What is the nature of the compound formed?
(b) State whether the compound formed will conduct electricity or not.
(c) Give the formula of the compound formed.
(d) What is the valency of element X?
(e) How many electrons are there in the outermost shell of an atom of element Y?

The following diagram shows a part of the periodic table containing first three periods in which five elements have been represented by the letters a, b, c, d and e (which are not their chemical symbols):

1

18

a	2	13	14	15	16	17
		b					c
d						e

(i) Select the letter which represents an alkali metal.
(ii) Select the letter which represents a nobles gas.
(iii) Select the letter which represents a halogen.
(iv) What type of bond is formed between a and e?
(v) What type  of bond is formed between d and e?

The elements A, B and C belong to groups 1, 14, and 17 respectively of the periodic table.
(a) Which two elements will form a covalent compound?
(b) Which two elements will form an ionic compound?

Find the neutral atom in the periodic table which has the same number of electrons as K⁺ and Cl⁻. What is this number?

Atoms of eight elements A, B, C, D, E, F, G and H have the same number of electron shells but different number of electrons in their outermost shells. It was found that elements A and G combine to form an ionic compound. This ionic compound is added in a small amount to almost all vegetables and dishes during cooking. Oxides of elements A and B are basis in nature while those of elements E and F acidic. The oxide of element D is, however, almost neutral. Based on the above information, answer the following questions:

(a) To which group or period of the periodic table do these elements belong?
(b) What would be the nature of compound formed by a combination of elements B and F?
(c) Which two of these elements could definitely be metals?
(d) Which one of the eight elements is most likely to be found in gaseous state at room temperature?
(e) If the number of electrons in the outermost shell of elements C and G be 3 and 7 respectively, write formula of the compound formed by the combination of C and G.

Write the names and symbols of two very reactive metals belonging to group 1 of the periodic table. Explain by drawing electronic structure, how either one of the two metals reacts with a halogen. With which name is the bond formed between these elements known and what is the class of the compound so formed known? State any four physical properties of such compounds.

The non-metal A is an important constituent of our food and most of the fuels around us. A forms two oxides B and C. The oxide B is poisonous whereas oxide C causes global warming.

(a) Identify A, B and C.
(b) To which group of periodic table does A belong?
(c) Name another element which is placed in the  same group as A.

A non-metal X which is the largest constituent of air combines with hydrogen when heated in the presence of iron as catalyst to form a gas Y. When gas Y is treated with sulphuric acid, it forms a compound Z which is used as a chemical fertiliser.

(a) What are X, Y and Z?
(b) To which group of periodic table does X belong?
(c) Name the periodic table in which X is placed.
(d) Which element is placed just before X in the period?
(e) Which element is placed just after X in the period?