Question

the table on the next page is made on the basis of the modern periodic table write in the electronic configuration of first 20 elements below the symbol and write the valency​

Answer 1

Hope it helps.............

Answer 2

Answer:

"The physical and chemical properties of the elements are periodic functions of their atomic numbers," is how the current Periodic law is best summarised. The number of protons or electrons in a neutral atom is equal to the atomic number.

Explanation:

A list of the first 20 elements below the symbol and their valency are as follows:-

Hydrogen[H]-valency- 1

Helium[He]-valency-0[noble gas]

Lithium[Li]-valency-1

Beryllium[Be]-valency-2

Boron[B]-valency-3

Carbon[C]-valency-4[it is a tetravalent element]

Nitrogen[N]-valency-3

Oxygen[O]-valency-2

Fluorine[F]-valency-1

Neon[Ne]-valency-0[noble gas]

Sodium[Na]-valency-1

Magnesium[Mg]-valency-2

Aluminium[Al]-valency-3

Silicon[Si]-valency-4[metalloid]/semi conductor

Phosphorus[P]-valency-3

Sulphur[S]-valency-2

Chlorine[Cl]-valency-1

Argon[Ar]-valency-0[noble gas]

Potassium[K]-valency-1

Calcium[Ca]-valency-2

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