Question

(a) (i) Give three main characteristics of representative elements.
(ii) Give the physical state of the last group members of the modern periodic table. State their valency.
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Answer 1

Answer:

(ii) the physical state of last group members of modern periodic table is gases and they all are inert gases. He ,Ne,Ar etc .

(I) these are inert gases are stable in nature

these gases has filled electronic outer shells

these gases used as to create vaccum during reaction

Answer 2

Let us look at the answer:

Explanation:

The modern periodic table is classified into 4 types:

• representative elements --- group 1,2 ,13-17
• transition elements ---- group 3-12
• inner transition elements ---- group 3 and period 6 and 7 (lanthanides and actinides)
• noble gases  ----- group 18

The three main characteristics of representative elements are:

• they consists of both metals and non-metals.
• They form electrovalent/ionic as well as covalent compounds.
• Metals in group 1 and 2 are good conductors of electricity.
• non-metals in group 16 and 17 are poor conductors of electricity.
• Few elements are heavier, like tin and lead which exhibit variable valency.
• Metallic character increases while moving down in all the seven groups.

The physical state of last group that is noble gases is gases.

• They are inert gases.
• They do not react with any elements.
• Their combining capacity , valency is 0.