Periodic Table Dalal New Simplified Class-9 ICSE Chemistry
by Dr Viraf J Dalal Middle School Chemistry Allied Publishers
Periodic Table Dalal New Simplified Class-9 ICSE Chemistry Solutions Chapter-5. We Provide Step by Step Solutions of Exercise/Lesson -5 The Periodic Table with Additional Questions , Previous Year Questions and Unit Test-5 of Dr Viraf J Dalal Middle School Chemistry Allied Publishers New Simplified Chemistry . Visit official Website CISCE for detail information about ICSE Board Class-9.
Periodic Table Dalal New Simplified Class-9 ICSE Chemistry Solutions Chapter-5
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New Simplified Chemistry Dalal Class-9 Solutions-The Periodic Table Previous Year Questions
State the number of elements in Period 1, Period 2, and Period 3 of the Periodic Table.
Period 1 is the shortest period has 2 elements Period 2 and 3 are short periods have 8, 8 elements.
What is the common feature of the electronic configuration of the elements at the end of Period 2 and Period 3 ?
The elements at the end of period have 8 electrons in valence shell.
Ne = 2, 8
Ar = 2, 8, 8
If an element is in Group 17 [or Group 7A] is it likely to be metallic or non- metallic in character ?
Element of group 17 or 7A has 7 electrons in valence shell hence non-metal.
Supply the missing word from those in brackets: If an element has one electron in its outermost energy level [shell] then it is likely to be [metallic / non- metallic].
Supply the missing word from those in brackets: If an element has one electron in its outermost energy level [shell] then it is likely to be metallic.
Copy and complete the following sentences choosing the correct word or words from those given in bracket at the end of each sentence :
The similarities in the properties of a group of elements is because they have the same ____ (electronic configuration, number of outer electrons, atomic numbers.)
The similarities in the properties of a group of elements is because they have the same electronic configuration.
What is meant by a Group in the Periodic Table.
Groups : “The verticle columns from top to bottom are called groups.”
How many elements are there in Period 2.
There are 8 elements in period 2.
Additional Questions of-The Periodic Table
(New Simplified Chemistry Dalal Class-9 )
What are elements. Give a reason why elements need to be properly classified.
Elements : “Are pure substances made up of one kind of atoms and cannot be broken down into simpler substances.” 118 elements are there.
Reason of classification of elements :
- It makes the study of elements in an organized manner.
- To help and correlate the properties of elements with the fundamental properties of different states of matter.
- To help to define the relationship of one element with others.
How did the early chemists classify elements.
Why was this basis of classification discarded for future classification of elements.
Early chemists classified the elements on the bases on their properties, nature, character, valency and whether they were metals or non-metals.
Basis of rejection :
- Some characteristics being considered, varied under different conditions.
- Certain elements resembled metallic as well as non-metallic both.
- It did not serve the purpose of classification.
What was Dobereiner’s basis,of classification of elements.
State Dobereiner’s Law of Triads with suitable examples.
Basis of classification was that “there was a close relationship between the properties of an element and its atomic mass”.
Dobereiner’s Law of Triads : “When elements are arranged in order of increasing atomic masses, groups of three elements (known as triads), having similar chemical properties are obtained. The atomic mass of the middle element of the triad being equal to the arithmetic mean of the atomic masses of the other two elements.”
- All of them are non-metals
- All have valency one (1).
- Each reacts with water to form acid.
Explain why Dobereiner’s method of classilication of elements did not hold much weightage for future classification.
Reasons for discarding the law of triads :
- Only three triads could be formed and was not holding for other elements.
- The law was not applicable even in the same family.
What was the basis of classification proposed by Newland.
State Newland’s Law of Octaves with a suitable example.
Newland – Basis of classification :
If elements are arranged in ascending order of their atomic masses every eighth element had properties similar to the properties of first element, just as eighth note of a musical octave is same as its first note.
Newland’s Law of Octaves :
“When elements are arranged in order of increasing atomic masses, the properties of every eighth element (starting from any element) are repetition of the properties of that starting element.
Li (first element)
Na (eighth element)
Properties of sodium are similar to lithium and that of Ca are similar to sodium.
In which way was Newland’s Law of Octaves comparable to a musical note.
As in above Question 5.
How did Mendeleeff arrange the elements in the periodic table.
What was the basis of his classification.
Mendeleeff arranged the elements in the increasing order of their atomic weights. Basis of classification was that properties of elements are periodic functions of their atomic weights.
i.e. “Elements with similar properties appear at regular intervals.”
State Mendeleeff’s Periodic Law.
How did Mendeleeff’s arrangement of elements correlate with periodicity of properties of elements.
Mendeleeff’s Periodic Law :
“Physical and chemical properties of elements are periodic function of their atomic masses.”
Every ninth element resembles in properties with first element and tenth element with second and so on. That is after regular interval. This means elements in the same vertical column the properties resemble.
State the contributions made by Mendeleeff towards the periodic table.
Contribution made by Mendeleeff :
- They were arranged in increasing order of atomic weights in horrizontal rows called periods in vertical columns called groups.
- Elements which are similar w.r.t. their chemical properties are grouped together and have atomic weights of nearly the same value.
- Elements in the same group had same valency and similar chemical properties.
- The properties of undiscovered elements left in the vacant gaps was predicted.
- In correct atomic weights of some of the arranged elements were corrected with the knowledge of the atomic weights of the adjacent elements.
- Number of gaps were left in the table for element not known at that time. Even predicted their properties by studying the properties of neighbouring elements. These elements were later on discovered and their properties were found to be corrects.
What were the defects and anomalies in Mendeleeff’s Periodic Table and how are they resolved by Moseley.