Question

An atom of an element is represented as 39/19x ,write its:
(i) Number of protons.
(ii) Number of neutrons.
(iii) Electronic configuration.
(iv) Number of valence electrons..

Answer 1

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Atomic number = Number of protons

Hence , number of protons in K atoms = 19

Number of neutrons = Mass number - Atomic number

Hence , number of neutrons in K atom = 39−19=20

Number of electrons = Number of protons

Hence , the number of electrons = 19

And electronic configuration of K atom = 2,8,8,1

Since K atom has 4 shells , hence it belongs to fourth period.

With one valence electron , it belongs to group 1

Number of protons in P atom = 15

Number of neutrons in P atom = 31−15=16

Number of electrons in P atom = 15

And electronic configuration of P atom = 2,8,5

Since it has three shells , it belong to period 3 and with 5 valence electrons Phosphorous is found in five plus ten that is 15

th

group.