Question

An element X having atomic no. 13 reacts with Y having atomic no. 9 to form a compound.Answer the following question based upon the above data.

1. Calculate the valency of X and Y.
2. What is the chemical formula formed between X and Y.
3. Which of the above is metal and which is a non-metal?
4. Why do X and Y react?

Answer 1

• Element having atomic no. 13 (X) - Aluminum (Al)
• Element having atomic no. 9 (Y) - Fluorine (F)

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(i) valency- it is the combining capacity of an element with other element by gaining , losing or sharing of electron to attain octet in outer most shell.

Way to find valency of an element-

1. To write electronic configuration.
2. No. of electron in outermost shell.
3. No. of electron required to complete outermost shell.

Valency of Aluminum (Al)

1. Electronic configuration- 2, 8, 3
2. No. of electrons in outermost shell- 3
3. No. of electron required to complete outer most shell- if 3 electrons lose by Aluminum then their octet will be complete.

Hence, Valency of Aluminum- 3

Valency of Fluorine (F)

1. Electronic configuration- 2, 7
2. No. of electrons in outermost shell- 7
3. No. of electron required to complete outer most shell- if one electron is gained by fluorine then its octet will be complete.

Hence, Valency of Fluorine - 1

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(ii) Chemical formula- AlF₃ (Aluminum fluoride)

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• metal- it is substance which is usually hard and shiny and heat and electricity can pass through.
• Non metals- They are those which lack all the metallic attributes. They are good insulators of heat and electricity. They are mostly gases and sometimes liquid.

(iii) Metal (X) - Aluminum

Non metal (Y) - Fluorine

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(iv) Al and F react to complete their stable configuration and form aluminum fluoride.