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Periodic Classification Of Elements Book Back Questions 9th Science Lesson 12

9th Science Lesson 12

12] Periodic Classification Of Elements

Book Back Questions with Answer and Do You Know Box Content

Choose the best answers:

1. If Dobereiner is related with ‘law of triads’, then Newlands is related with

(a) Modern 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

Fill in the blanks:

1. In Dobereiner’s triads, the atomic weight of the middle elements 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 _________________.

Match the following:

1. Triads – Newlands

2. Alkali metal – Calcium

3. Law of octaves – Henry Moseley

4. Alkaline earth metal – Sodium

5. Modern Periodic Law – Dobereiner

State true or false. If false, correct the statement:

1. Newland’s periodic table is based on atomic masses of elements and modern periodic table is based on atomic number of elements.

2. Metals can give electrons.

3. Alloys bear the characteristics of both metals and non-metals.

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.

Consider the statements given below and choose the correct option:

Statement: Elements in a group generally posse’s 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.

Answers:

Choose the best answers:

1. Law of octaves 2. atomic numbers 3. 18, 7

Fill in the blanks:

1. Average 2. 18th 3. Atomic masses 4. Mercury

Match the following:

1.Triads- Dobereiner

2.Alkali metal- Sodium

3.Law of octaves- Newlands

4.Alkaline earth metal- Calcium

5.Modern Periodic Law- Henry moseley

State true or false. If false, correct the statement:

1.True

2.False

Correct answer: Metals tends to lose electrons to attain noble electron configuration

3.False

Correct answer: An alloy is a mixture of both metals

4.True

5.True

Consider the statements given below and choose the correct option:

1.Statement is true and reason explains the statement

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