Question

the atomic number of an element X is 20. write
• its valency
• whether it is a metal or non metal
• the formula of compound formed when element X reacts with element Y of atomic number 8
pls ans fast

Answer 1

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Here is Your Answer..!!
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↪Actually welcome to the concept of the Chemistry.

↪Basically the Element having the atomic number 20 is the CALCIUM..

↪Thus The electronic Configuration of CALCIUM is ( 2,8,8,2)

↪thus it has 2 electrons in its valence shell ...

↪Thus this Indicates that it has the VALENCY AS +2

↪CALCIUM is Electropositive in nature ..thus it's a METAL ..

↪WHEN THE CALCIUM reacts with the element having atomic number 8 that is OXYGEN ...

↪since the oxygen has the VALENCY AS -2 ...

↪Thus the compound formed is CaO

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Answer 2

Solutions :-

We know that,

Valency ➠ Number of electron lose, gain or shared by an atom/element is known as its valency.

Valence shell ➠ Outer most shell of an atom is called Valence shell.

Valence Electron ➠ Number of electron present in the valence shell is called Valence electron.


For metal valence electron are 1, 2 & 3
For non-metal valence electron are 4, 5, 6 & 7
For Noble gas valence electron is 8


Given :
The atomic number of an element X is 20.


Find its valency :-

By electronic configuration we get,

K shell = 2
L shell = 8
M shell = 8
N shell = 2

So, Valency = 2


Find whether it is a metal or non metal :-

Here, Valence electron is also 2

As we know that the elements which has valence electron is 2, That is metal.

So, It is Metal



Now,
Find the compound formed when element X reacts with element Y of atomic number 8 :-

We know,

Atomic number of X is 20. i.e.., Calcium.
Atomic number of Y is 8. i.e.., Oxygen

Calcium reacts with Oxygen =>

Ca + O => CaO


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✯ @shivamsinghamrajput ✯