Selina solutions for Concise Chemistry [English] Class 9 ICSE chapter 5 - The Periodic Table [Latest edition]

What is the need for classification of elements?

What was the basis of the earliest attempts made for classification and grouping of elements?

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

Why was Dobereiner's triad discarded?

Explain 'Newland's Law of Octaves.' Why was the law discarded?

Did Dobereiners triads also exist in the columns of Newland's Octaves? Compare and find out.

Lithium, sodium, and potassium elements were put in one group on the basis of their similar properties. What are those similar properties?

The elements calcium, strontium and barium were put in one group or family on the basis of their similar properties.

What were those similar properties?

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

Mendeleev's contributions to the concept of a periodic table laid the foundation for the Modern Periodic Table. Give reasons.

State Mendeleev’s periodic law.

Use Mendeleev's Periodic Table to predict the formula of hydrides of carbon and silicon.

Use Mendeleev's Periodic Table to predict the formula of oxides of potassium, aluminum, and barium.

Which group of elements was missing from Mendeleev's original periodic table?

How the reaction can proceed continuously? 

State the merits of Mendeleev's classification of elements.

Why did Mendeleev's leave some gaps in his periodic table os elements? Explain your answer with an example.

The atomic number of an element is more important to the chemist than its relative atomic mass. Why?

Consider the following elements: Be, Li, Na, Ca, K. Name the elements of (a) same group (b) same period.

Name an element whose properties were predicted on the basis of its position in Mendeleev's periodic table.

Name two elements whose atomic weights were corrected on the basis of their positions in Mendeleev's periodic table.

How many elements were known at the time of Mendeleev's classification of elements?

State the modern periodic law.

How many periods and groups are there in the modern periodic table?

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

What is meant in the periodic table by a group?

What is meant in the periodic table by a period?

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

What are the following group known as?

Group 1

What are the following group known as?

Group 17

What are the following group known as?

Group 18 

Name two elements of each group.

What is the number of elements in the 1^st period?

What is the number of elements in the 3^rd period, of the modern periodic table?

How does number of valence electrons vary on moving from left to right in the third period of a periodic table?

How does number of (i) valence electrons (ii) valency; vary on moving from left to right in the second period of a periodic table?

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

This question refers to elements of the periodic table with atomic numbers from 3 to 18. In the table below, some elements are shown by letters, even though the letters are not the usual symbols of the elements.

Which of these is:

1. a noble gas?
2. a halogen?
3. an alkali metal?
4. an element with valency 4?

This question refers to elements of the periodic table with atomic numbers from 3 to 18. In the table below, some elements are shown by letters, even though the letters are not the usual symbols of the elements.

If A combines with F, what would be the formula of the resulting compound?

This question refers to elements of the periodic table with atomic numbers from 3 to 18. In the table below, some elements are shown by letters, even though the letters are not the usual symbols of the elements.

What is the electronic configuration of G?

Sodium and aluminum have atomic numbers 11 and 13, respectively. They are separated by one element in the periodic table and have valencies 1 and 3 respectively. Chlorine and potassium are also separated by one element in the periodic table (their atomic numbers being 17 and 19, respectively) and yet both have valency 1. Explain.

Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common.

 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?

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

The position of elements A, B, C, D and E in the periodic table are shown below:

State which is metals, non-metals, and noble gas in this table.

The position of elements A, B, C, D and E in the periodic table are shown below:

State which is most reactive (i) metal (ii) non-metal

The position of elements A, B, C, D and E in the periodic table are shown below:

Which type of ion will be formed by elements A, B, and C.

 The position of elements A, B, C, D and E in the periodic table are shown below:

Which is larger in size (i) D or E (ii) B or C

Write the electronic configuration of element ₁₇T³⁵.

1. What is the group number of T?
2. What is the period number of T?
3. How many valence electrons are there in an atom of T?
4. What is the valency of T?
5. Is it a metal or non-metal?
6. State number of protons and neutrons in T.

Element P has atomic number 19. To which group and period, does P belong? Is it a metal or a non-metal? Why?

An element belongs to the third period and Group IIIA (13) of the periodic table. State: the number of valence electrons,

An element belongs to the third period and Group IIIA (13) of the periodic table. State: the valency,

An element belongs to the third period and Group IIIA (13) of the periodic table. State: if it is a metal or non-metal?

An element belongs to the third period and Group IIIA (13) of the periodic table. State: the name of the element. 

Name and state the following with reference to the elements of the first three periods of the periodic table.

Noble gas with duplet arrangement of electrons.

Name and state the following with reference to the elements of the first three periods of the periodic table.

Metalloid in Period 3.

Name and state the following with reference to the elements of the first three periods of the periodic table.

Valency of elements in Group 14 and 15.

Name and state the following with reference to the elements of the first three periods of the periodic table.

Noble gas having electronic configuration: 2, 8, 8.

Name and state the following with reference to the elements of the first three periods of the periodic table.

Group whose elements have zero valencies.

Name and state the following with reference to the elements of the first three periods of the periodic table.

A covalent compound formed by an element in period 2 and a halogen.

Name and state the following with reference to the elements of the first three periods of the periodic table.

Non-metallic elements present in Period 3 of Groups 15 and 16.

Name and state the following with reference to the elements of the first three periods of the periodic table.

An electrovalent compound formed by an alkaline earth metal and a halogen.

Name and state the following with reference to the elements of the first three periods of the periodic table.

Bridge elements of Period 3 of Group 1,2 and 3.

Name and state the following with reference to the elements of the first three periods of the periodic table.

Alkali metal in period 3 dissolves in the water giving a strong alkali.

Name and state the following with reference to the elements of the first three periods of the periodic table.

Typical elements of Groups 14 and 15.

Name and state the following with reference to the elements of the first three periods of the periodic table.

Alkaline earth metal in period 3.

Match column A with column B.

Complete the table:

Relative atomic mass of a light element up to calcium is approximately ______ its atomic number.

The horizontal rows in a periodic table are called _____.

Going across a period left to right, atomic size _____.

Moving left to right in the second period, the number of valence electrons _____. 

Moving down in the second group, number of valence electrons ______.

Name the alkali metals, How many electron(s) they have in their outermost orbit.

Take any one alkali metal and write its reaction with (i)oxygen (ii)water (iii)acid.

Name the method by which alkali metals can be extracted.

What is the colour of the flame of sodium and potassium?

An element A has 2 electrons in its fourth shell. State:

its atomic number

An element A has 2 electrons in its fourth shell. State its electronic configuration.

An element A has 2 electrons in its fourth shell. State:

its valency

An element A has 2 electrons in its fourth shell. State:

position in the periodic table

An element A has 2 electrons in its fourth shell. State:

is it a metal or non-metal

An element A has 2 electrons in its fourth shell. State:

is it an oxidising or reducing agent 

Name the first three alkaline earth metals.

Write the reactions of the first three alkaline earth metals with dilute hydrochloric acid.

Write the electronic configuration of the first two alkaline earth metals.

How do alkaline earth metals occur in nature?

 Give reason:

Alkali metals are kept in an inert solvent.

 Give reason:

Alkali metals and halogens do not occur free in nature.

 Give reason:

Alkali and alkaline earth metal compounds usually form electrovalent compounds.

 Give reason:

Inert gases do not form compounds.

Arrange the following:

Elements of group 1, in increasing order of reactivity

Arrange the following:

Elements of group 17, in decreasing order of reactivity

Arrange the following:

He, Na, Mg ( increasing order of melting point)

Arrange the following:

Chlorine, sodium, magnesium (increasing reducing character)

State the nature of compounds formed when group 17 elements combine with (i) metals (ii) non-metals.

Why group 17 elements are highly reactive?

How many electrons do inert gases have in their valence shells?

Name an element of group 18 which can form compounds.

Name the gas used in:

Filling balloons

Name the gas used in:

Light bulbs

Name the gas used in:

Bright colour advertising light works

What is the name given to group 17 elements? Why are they called so?

Comment on the (i) reactivity (ii) colour (iii) physical state of group 17 elements.

Two elements P and Q belong to the same period of the modern periodic table and are in group 1 and group 2, respectively. Compare the following characteristics in the tabular form.

1. Number of electrons in their atoms
2. Their tendency to lose electrons
3. Their metallic characters
4. Formation of their oxides
5. Formulae of their chlorides