Periodic Classification of Elements

Samacheer Book Back Questions And Answers For Science Standard 9 “Periodic Classification of Elements“

I. Choose the correct answer:
1. If Dobereiner is related with ‘law of triads’, then Newlands is related with
(a) Modem periodic law
(b) Hund’s rule
(c) Law of octaves
(d) Pauli’s Exclusion principle

2. Modern periodic law states that the physical and chemical properties of elements are the periodic functions of their _____.
(a) atomic numbers
(b) atomic masses
(c) similarities
(d) anomalies

3. Elements in the modern periodic table are arranged in _____ groups and _____ periods.
(a) 7, 18
(b) 18, 7
(c) 17, 8
(d) 8, 17

II. Fill in the blanks:
1. In Dobereiner’s triads, the atomic weight of the middle element is the _____ of the atomic masses of 1st and 3rd elements.
2. Noble gases belong to _____ group of the periodic table.
3. The basis of the classifications proposed by Dobereiner, Newlands and Mendeleev was _____.
4. Example for liquid metal is _____.

Answers:
1. average
2. 18th
3. atomic mass
4. mercury

III. Match the following:
1. Triads                             A. Newlands
2. Alkali metal                    B. Calcium
3. Law of octaves              C. Henry Moseley
4. Alkaline earth metal      D. Sodium
5. Modern Periodic Law    E. Dobereiner

Answers:
1. E
2. D
3. A
4. B
5. C

IV. State whether true or false. If false, correct the statement:
1. Newlands’ periodic table is based on atomic masses of the elements and modern periodic table is based on atomic number of elements.
2. Metals can gain electrons.
3. Alloys bear the characteristics of both metals and nonmetals.
4. Lanthanides and actinides are kept at the bottom of the periodic table because they resemble each other but they do not resemble with any other group elements.
5. Group 17 elements are named as Halogens.

Answers:
1. True
2. False (Metals tend to lose electrons)
3. False (Metalloids bear the characteristics of both metals and nonmetals)
4. True
5. True

V. Assertion and reason type questions:
1. Statement: Elements in a group generally possess similar properties but elements along a period have different properties.
Reason: The difference in electronic configuration makes the element differ in their chemical properties along a period.
a) Statement is true and reason explains the statement.
b) Statement is false but the reason is correct.

Visit Our YouTube Channel For More Free Videos: Click Here