This chapter is from Module 2 Matter in Our Surroundings. This post provides you complete answer of all intext and terminal questions given in Chapter 6- Periodic Classification of Elements from Subject Code 212.
Our experienced teachers have provided
easy and accurate answers to all questions that will help you complete your assignments. You can also solve the worksheet 6 based on this chapter.
Periodic Classification of Elements - Overview
In this lesson form
NIOS class 10 Science, students will gain the knowledge about elements and
their classification on the basis of their atomic mass and atomic number.
This post provides you complete solutions of
intext and terminal exercise questions in detail.
|
Board |
NIOS |
|
Subject |
Science & Technology |
|
Subject Code |
212 |
|
Module |
2- Matter in Our Surroundings |
|
Chapter |
Periodic Classification of Elements |
|
No. of Intext questions |
10 |
|
No. of Terminal Exercise
questions |
72 |
Intext Questions 6.1 with Answers
Q1. Elements A, B and C constitute a
Dobereiner’s traid. The atomic mass of A is 20 and that of C is 40. Predict the
atomic mass of B.
Answer
According to Dobereiner, The atomic mass
of the middle element was roughly the average of the atomic masses of the other
two elements.
Atomic
mass of B = 30
Q2. Which property of atoms was used by Mendeleev
to classify the elements?
Answer
Mendeleev
classified the elements on the basis of ‘ Atomic mass’.
Q3. In Mendeleev’s periodic classification,
whether chemically similar elements are placed in a group or in a period?
Answer
Mendeleev placed elements similar in
chemical properties in group (coloumn).
Q4. Mendeleev’s periodic table had some
blank spaces. What did they signify?
Answer
Mendeleev left some gaps in his table
because he predicted the properties of new elements that had not been
discovered at that time. e.g.-He named them by prefixing a Sanskrit numeral 'Eka' .Scandium, gallium and germanium discovered later have properties similar to
eka-boron, eka- aluminium and eka-silicon.
Q5. Explain any three defects of Mendeleev’s
periodic table?
Answer
1. Position
of Hydrogen
Mendeleev could not give proper position
to hydrogen. Electronic configuration of hydrogen resembles that of alkali
metals and hydrogen also exist as diatomic molecule like halogens.
2. Position
of Isotopes
Isotopes of an element have similar
properties that of the element but have different atomic mass so according to
increasing order of atomic masses, they should be placed in different groups
but Mendeleev could not give them proper place.
3. Wrong
Order of Elements
He arranged the elements according to in
order of increasing atomic masses but at number of places this order was not
followed.e.g.- Co ( 58.93) is placed before Ni ( 58.71) & Te (127.60) is
placed before I (126.90).
These are the main three defects, you can
also include the following
4. Dissimilar
Elements in one group
He placed dissimilar elements in the same
group.e.g.- Li,K,Rb & Cs of group IA have no similarity with Cu,Na,Ag &
Au of group IB but they are placed under I group.
5. He
made no attempt to separate metals and non-metals.
Intext Questions 6.2 with Answers
Q1. Give any two defects of Mendeleev’s
periodic table which has been removed in the moderns periodic table. How were
they removed?
(i) Wrong order of elements
Mendeleev placed the elements with higher atomic mass (Argon-40) before
those with lower atomic mass (Potassium -39).
Elements are arranged on the basis of increasing order of atomic numbers so all elements were arranged in proper order.
(ii) Place of Isotopes
Mendeleev
arranged elements on the basis of atomic mass so isotopes of same element (have
different atomic masses) could not be placed at the same position.
But Modern periodic table is based on
atomic number. Since all isotopes of an element have same atomic number so they
were placed at the same position.
Q2. Metalloids are present along the diagonal
line starting from group 13 and going down to group 16. Do they justify their
position in the modern periodic table?
Answer
Metalloids have properties intermediate
between metals and non-metals. They justify their position in the modern periodic
table as they separate metals from non-metals.
Their position also shows a gradual
transition in chemical and physical properties.
Intext Questions 6.3 with Answers
Q1. Fill in the blanks with appropriate words:
(a) The force of attraction between nucleus and valence electrons ……………….in a period from left to right.
(b) Atomic radii of elements ………………….in a period from left to right.
(c) Atomic radii of elements in a group from top to bottom.
(d) Metallic character of elements ……………. from top to bottom in a group.
Answer
(a)
Increases
(b)
Decreases
(c)
Increases
(d)
Increases
Q2. In the following crossword puzzle,
elements are present horizontally, vertically downwards and diagonally
downwards. Let us find out how many elements you are able to get within 5
minutes.
Please check in the intext answers to find if you missed out any.
Answer
Horizontally → hydrogen, carbon, Barium,
Sodium , Boron, Chlorine
Vertically →Magnesium , Iodine , Helium ,
Neon , Silicon
Diagonally downwards → Nitrogen , Oxygen,
Q3. Let us find how many riddles you can solve.
(i) I am the only noble gas whose outermost shell has 2 electrons, who am I?
(ii) I am placed in group 16 of the modern periodic table and essential for your respiration, who am I?
(iii) I combine with chlorine to form your table salt, who am I?
Answer
(i) Helium
(ii) Oxygen
(iii) Sodium
Terminal Exercise Questions with Answers
A). Objective Questions
I. Mark the correct choice:
1. Which one of the following was the earliest attempt of classification of elements?
a. Classification of elements into metals and non-metals
b. Newlands’ law of Octaves
c. Dobereiner’s Traids
d. Mendeleev’s Periodic Table
Correct answer – (a) Classification of
elements into metals and non-metals
Explanation : The first classification of
elements was into two groups – Metals and non-metals
2. The ‘law of octaves’ was given by
a. Mandeleev
b. Newlands
c. Lother Meyer
d. Dobereiner
Correct answer – (b) Newlands
3. According to the periodic law given by Mendeleev, the properties of an element are a periodic function of its
a. Atomic volume
b. Atomic size
c. Atomic number
d. Atomic mass
Correct answer – (d) Atomic mass
4. The particle which is universally present in the nuclei of all elements is
a. Neutron
b. Proton
c. Electron
d. α – particle
Correct
answer – (b) Proton
5. Potassium is more metallic than sodium because
a. both have 1 electron in their outermost shell
b. both are highly electropositive
c. sodium is larger in size than potassium
d. potassium is larger in size than sodium
Correct answer – (d) Potassium is
larger in size than sodium
6. Which one of the following elements in its chloride does not show the valence equal to its valence electrons?
a. NaCl
b. MgCl2
c. AlCl3
d. PCl3
Correct answer – (d) PCl3
7. Which one of the following elements has the least tendency to form cation?
a. Na
b. Ca
c. B
d. Al
8. Which one of the following does not belong to the family of the alkali metals?
a. Li
b. Na
c. K
d. Be
Correct
answer – (d) Be
9. The number of elements in the 5th group of the periodic table is
a. 2
b. 8
c. 32
d. 18
Correct
answer – (d) 18
10. The elements with atomic number 9 resemble with the elements having atomic number
a. 35
b. 27
c. 17
d. 8
Correct answer – (c) 17
11. In which period of the periodic table, an element with atomic number 20 is placed?
a. 4
b. 3
c. 2
d. 1
Correct answer – (a) 4
II. Mark the following statements True(T) or False (F):
2.
The
vertical columns in the periodic table are called periods.
3.
Mendeleev
depended only on the atomic mass of elements for his classification.
4.
All
elements present in a group are chemically similar.
5.
The
modern periodic law is based upon at atomic mass.
6.
The
importance of atomic number as the fundamental property was realised by Henry
Mosely.
7.
There
are 18 groups in the modern periodic table.
8.
Non
– metals are present in the middle portion of the periodic table.
9. Each period in modern periodic classification begins with filling of electron in a new shell.
Answer
1. The properties of
the middle element in a Dobereiner’s traids are intermediate between those of the
other two.(T)
2. The vertical
columns in the periodic table are called periods.(F)
3. Mendeleev depended
only on the atomic mass of elements for his classification.(F)
4. All elements
present in a group are chemically similar.(T)
5. The modern
periodic law is based upon at atomic mass.(F)
6. The importance of
atomic number as the fundamental property was realised by Henry Mosely.(T)
7. There are 18 groups
in the modern periodic table.(T)
8. Non – metals are
present in the middle portion of the periodic table.(F)
9. Each period in
modern periodic classification begins with filling of electron in a new shell.(T)
III. Fill in the blanks:
2.
The
……………….number is same as the number of shell which in gradually filled up in the
elements of this period.
3.
In
normal elements of a particular period the electrons are gradually filled in ………………shell.
4.
All
elements of a particular group have ……….electronic configurations.
5.
In
the modern periodic table, groups are numbered from …………….to ………………
6.
The
second and third periods of the periodic table are called ………………periods.
7.
The
main group elements are present in group 1 and 2 on the left side and …………….to…………….
on the right side of the periodic table.
8.
All
the group eighteen elements (except the first one) contain ……………valence
electrons.
9.
All
transition elements are metals with …………melting and boiling points.
10. The
groups of 14 rare earth elements belonging to the group 3 and 7th period
are called………………
11. All
elements present in a given ……………..have the same valency.
12. Atomic
size …………….in a period from left to right.
13. Magnesium
is ……………….metallic than calcium.
14. Carbon
belongs to group …………………of the periodic table.
15. All
the elements of group 15 have ………………valence electrons.
Answer
1. According
to the modern periodic law, the properties of elements are periodic function of
their atomic number.
2. The
period number is same as the number of shell which in gradually
filled up in the elements of this period.
3. In
normal elements of a particular period the electrons are gradually filled in outermost
shell.
4. All
elements of a particular group have similar electronic
configurations.
5. In
the modern periodic table, groups are numbered from 1 to 18.
6. The
second and third periods of the periodic table are called short periods.
7. The
main group elements are present in group 1 and 2 on the left side and 13
to 18 on the right side of the periodic table.
8. All
the group eighteen elements (except the first one) contain 8 valence electrons.
9. All
transition elements are metals with high melting and boiling
points.
10. The
groups of 14 rare earth elements belonging to the group 3 and 7th period are
called actinides.
11. All
elements present in a given group have the same valency.
12. Atomic
size decreases in a period from left to right.
13. Magnesium
is less metallic than calcium.
14. Carbon
belongs to group 14 of the
periodic table.
15. All
the elements of group 15th have 5
valence electrons.
B). Subjective Questions
I. Very short Answer Questions (Answer in one word or one statement)
Q1. What was the earliest classification of elements?
Answer
The earlies classification of elements is Metals and Non-metals.
Q2. State Newlands’ law of octaves.
Answer
Every eight element had properties similar to that of the first element when arranged in increasing order of atomic mass.
Q3. Which classification of elements failed after the discovery of noble gases?
Answer
Mendeleev’s Periodic Classification
Q4. State Mendeleev’s Periodic Law.
Answer
The properties of elements are the periodic function of their atomic masses (weight).
Q5. How were the groups numbered in the Mendeleev’s periodic table?
Answer
Groups were numbered from I to VIII
Q6. Name the fundamental properties of elements on which the modern periodic law is based.
Answer
Atomic Number
Q7. How many groups are there in the modern periodic table?
Answer
There are 18 groups in the modern periodic table.
Q8. How have groups been numbered in the modern periodic table?
Answer
Groups have been numbered 1 to 18.
Q9. What are normal elements?
Answer
Elements of s block and p block are normal elements.
Q10. What are the elements present in the middle portion of the modern periodic table called?
Answer
Transition elements
Q11. What is atomic size?
Answer
The distance between nucleus and outermost shell.
Q12. How does atomic size vary in a period and in a group?
Answer
Atomic size decreases in a period and increase in a group.
Q13. Where would the element with largest atomic size be placed in any group?
Answer
At the bottom in any group.
Q14. Give the number of a group in which metallic, metalloid and non-metallic, all three types of elements are present.
Answer
In the group 14
II. Short Answer Questions (Answer in 30-40 words)
Q1. State
Dobereiner’s law of traids.
Answer
He classified the known elements in groups
of three elements on the basis of similarities in their properties. These
groups are called triads. The atomic mass of the middle element was roughly the
average of the atomic masses of the other two elements.
Q2. Show that chlorine,
bromine and iodine (atomic 35.5, 80 and 127 respectively) constitute a traid.
Answer
Atomic mass of bromine is approx 80.
Q3. What were
the reasons for the failure of Newlands’ law of octaves?
Answer
He could identify only three triads from
the elements known at that time. This system of classification was not found to
be useful.
Q4. Describe
Mendeleev’s periodic table briefly innermost rows and columns and their raw
being.
Answer
Horizontal columns were called periods and
vertical columns were called groups. Groups from I to VIII were further divided
into two sub groups – A & B. There were total eight groups and seven
periods in the table.The first six periods were complete and the seventh was
incomplete.
Q5. Give any
two achievements of the Mendeleev’s periodic classification.
Answer
1.Mendeleev
classified the elements on the fundamental basis i.e. atomic mass.
2. He left some gaps in his table because
he predicted the properties of new elements that had not been discovered at
that time.e.g.-He named them by prefixing a Sanskrit numeral
Eka.Scandium,gallium and germanium discovered later have properties similar to
eka-boron,eka-aluminium and eka-silicon.
Q6. What were
the defects in Mendeleev’s periodic classification.
Answer
1. Isotopes of an element have similar
properties that of the element but have different atomic mass so according to
increasing order of atomic masses, they should be placed in different groups
but Mendeleev could not give them proper place.
2.He arranged the elements according to in
order of increasing atomic masses but at number of places this order was not
followed.e.g.- Co ( 58.93) is placed before Ni ( 58.71) & Te (127.60) is
placed before I (126.90).
Q7. State
Modern periodic law.
Answer
The properties of elements are periodic
function of their atomic numbers.
Q8. Briefly
describe the modern periodic table in terms of groups and period.
Answer
1.Elements
are arranged in the table according to ascending atomic number.
2.Elements
are arranged in periods and groups.
3.There
are seven periods and 18 groups in the table.
4.Elements
are arranged in periods according to increasing atomic number.
5.Elements
in a group have similar electrons in their outer most shell.
Q9. Give names
of four classes into which the elements have been classified and mention to
which groups of the modern period table they belong.
Answer
Elements are classified into the following four classes:
1. Noble gases -Group 18
2. Normal elements (Metals and non- metals)- Groups 1,2 and 13 to 17
3. Transition elements – Group 3 to 12
4. Inner transition elements – Lanthanides and Actinides – F block
Q10.List the
merits of the long form of the modern periodic table and explain any two of
them.
Answer
Following are the merits of modern
periodic table
1. Position of isotopes
2. Anomalous pairs
3. Electronic
configuration
4. Separation of
metals and non-metals
5. Position of transition elements
(1) Position of isotopes – All isotopes of an element have same atomic number so they all occupy the same position in the modern periodic table.
(2) Anomalous Pairs – In the Mendeleev’s periodic table , heavier element (Co- ) was placed before the lighter element (Ni-)
Q11.How are
the electronic configurations of all the elements belonging to a particular
group related? Explain with the help of group 17 elements.
Answer
Elements in the modern periodic table were
arranged in increasing order of atomic number. Elements in the same particular group
have similar valence electrons in the outermost shell.
General outer electronic configuration of
elements of 17 group is ns2np5
Q12.How does
the electronic configurations of elements to a particular period vary? Explain
with the examples of second periods elements.
Answer
The electronic configuration of elements
in a particular period vary in number of valence electrons but the number of
shells remains the same in a period.
Example of Second Period
All elements have two shells.
Q13. Define
atomic radius.
The distance
between the centre of nucleus and outermost shell is known as atomic radius. It
also indicates the size of an atom and measured in picometres or angstroms.
Atomic radius decreases across a period
and increases across a group in the periodic table.
Q14. How and
why does metallic character vary in a group from top to bottom?
Answer
Metallic character: - The tendency of losing
electrons form outermost shell and form cation (+ve ions), is called metallic
character.
Metallic character increases in a group
from top to bottom
Reason:
Due to
increase in atomic size and decrease in effective nuclear attraction, atoms loss
or donate electrons easily , that’s why metallic character increases in a group
from top to down.
III. Long Answer Questions (Answer in 60-70 words)
Q1. State Mendeleev’s Periodic Law and describe the periodic
table constructed on this basis.
Answer
Mendeleev’s
periodic law: - The properties of elements are the periodic function of their atomic
masses (weight).
Mendeleev’s
periodic table
1.Mendeleev arranged all the known 63 elements
in the increasing order of their atomic masses.
2.Horizontal columns were called periods and
vertical columns were called groups.
3.Groups from I to VIII were further divided
into two sub groups – A & B.
4.There were total eight groups and seven
periods in the table.
5.The first six periods were complete and the
seventh was incomplete.
Q2. What are the merits and demerits of the Mendeleev’s
Periodic classification?
Answer
Merits of Mendeleev’s Periodic Table
1.Mendeleev classified the elements on the
fundamental basis i.e. atomic mass.
2.It was easy to study the properties of
elements because elements were present in dame sub group show similar
properties.
3.He left some gaps in his table because he
predicted the properties of new elements that had not been discovered at that
time.e.g.-He named them by prefixing a Sanskrit numeral Eka.Scandium,gallium
and germanium discovered later have properties similar to
eka-boron,eka-aluminium and eka-silicon.
Demerits of Mendeleev’s Periodic Table
1.Mendeleev could not give proper position to
hydrogen. Electronic configuration of hydrogen resembles that of alkali metals
and hydrogen also exist as diatomic molecule like halogens.
2.Isotopes of an element have similar
properties that of the element but have different atomic mass so according to
increasing order of atomic masses, they should be placed in different groups
but Mendeleev could not give them proper place.
3.He arranged the elements according to in
order of increasing atomic masses but at number of places this order was not
followed.e.g.- Co ( 58.93) is placed before Ni ( 58.71) & Te (127.60) is
placed before I (126.90).
4.He placed dissimilar elements in the same
group.e.g.- Li,K,Rb & Cs of group IA have no similarity with Cu,Na,Ag &
Au of group IB but they are placed under I group.
5.He made no attempt to separate metals and
non-metals.
Q3. Describe the modern periodic table in term of group and
periods.
Answer
Modern Periodic Table: -
1.Elements are arranged in the table according
to ascending atomic number.
2.Elements are arranged in periods and groups.
3. There are seven periods and 18 groups in the
table.
4.Elements are arranged in periods according
to increasing atomic number.
5.Elements in a group have similar electrons
in their outer most shell.
Description of Modern Periodic Table: -
Modern
periodic table has seven periods and eighteen groups. Horizontal rows are known
as periods and vertical columns are known as groups.
There are
eighteen groups in the modern periodic table. These groups are divided in four
blocks named s,p,d, & f. The element in the certain block sows its valence
electron in the same block.e.g. Elements in block “s” have their valance
electrons in s orbital.
Q4. What are the following types of elements and where are they located in the periodic table?
(a) Mian group elements
(b) Noble gases
(c) Transition elements
(d) Inner transition elements
Answer
(a) Main group elements – These elements are also called representative elements including alkali metals, alkali earth metals & halogens etc.
Position :- These elements are present in group 1,2 and 13 to 17 in s and p blocks in the modern periodic table.
(b) Noble gases- These elements have completely filled outermost shells and they are unreactive; they are called noble or inert gases. Ex- He, Ne, Kr etc.
Position: - These noble gases are present in group 18.
(c) Transition elements- These elements have partially filled d- orbital and they represent transition from the most electro positivity to the most electronegativity, so they are called transition elements.
Position:-These elements are present in group from 3 to 12 in d block.
(d) Inner Transition elements – These elements are called rare earth elements. They are two series of 14 elements – (i) Lanthanoids (ii) Actinoids
Position: - These are present in f- block.
Lanthanoids are in group 3 and period 6. Actinoids are in group 3 and period 7.
Q5. Discuss the merits of the modern periodic table.
Answer
The modern
periodic table removed the defects of Mendeleev’s periodic table and these are
merits of modern periodic table.
1. Position of isotopes – All isotopes
of an element have same atomic number so they can occupy same position in the table.
2. Separation of
Metals and non-metals – Metals are placed at the left side and non-metals are
at right side of the table. They are separated by metalloids.
3. Anomalous pairs-
Elements are arranged on the basis of increasing order of atomic number so the
anomalous pairs defect of Mendeleev’s periodic table is removed. Ex- Ni (A.N.-28)
is placed before Co (A.N.- 29).
4. Position of
transition elements- These elements have been allotted clear separate position
in the table.
Q6. What is the relationship between the electronic configuration
and the modern periodic table?
Answer
The modern
periodic table based on the atomic number and elements were arranged on the
basis of increasing order of atomic number.
The
elements have certain pattern of electronic configuration are placed in the
same group. All elements in the same group have similar chemical properties. So
the position of elements in the table is directly related to the electronic
configuration.
Q7. Explain the variation of atomic size in a group and in a
period.
Answer
Atomic size (atomic radii):- Atomic size of an element is measured by radius of atom. The distance
between nucleus and the outermost shell of the atom.
In Period
The atomic
radius decreases in moving left to right along the period because nuclear
charge increase which tends to pull the electrons closer to the nucleus and
reduce the size of the atom.
In Group
The atomic
radius increases in moving down the group because new shells are being added.
This increases the distance between the outermost electrons and the nucleus.
Q8. How is metallic character related to ionization energy? Explain
variation of metallic character in the periodic table.
Answer
Metallic character – The tendency
of losing electrons from outermost shell and form positive ions is called metallic
character.
Ionization energy – The minimum
energy required to remove an electron from an atom is called ionization energy.
Relation between metallic character and ionization energy
Both have
inverse relation between them. Lower ionization energy means higher metallic
character.
Metals have
low ionization energy so that they lose electrons easily.
Variation of metallic character in the periodic table.
Metallic
character decreases in a period and increases in a group.
As we move from left to right in a particular period,
effective attraction force on electron in the outermost shell increases so
elements cannot lose electrons easily.
While on
moving top to downward in a group, the force decreases and number of shells increases
so element(metal) can lose electrons easily.
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