Allied solutions

Allied solutions

Grade 8

Atomic Structure | Exercise

Question 10

Q10) If an atom has atomic number 19 & mass number 39, state -

  1. It’s electronic configuration
  2. The number of valence electrons it possesses

Solution :

Atomic number = 19

Number of protons = Number of electrons = 19

Mass number = Number of protons + Number of neutrons

39 = 19 + N

N = 20

Electronic configuration

19 = (2, 8, 8, 1)

Electrons in K shell (1st) = 2

Electrons in L shell (2nd) = 8

Electrons in M shell (3rd) = 8

Electrons in N shell (4th) = 1

Valence electrons is the number of electrons in the outer shell, i.e. 1 in this atom.

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subject-cta

Question 10

Q10) If an atom has atomic number 19 & mass number 39, state -

  1. It’s electronic configuration
  2. The number of valence electrons it possesses

Solution :

Atomic number = 19

Number of protons = Number of electrons = 19

Mass number = Number of protons + Number of neutrons

39 = 19 + N

N = 20

Electronic configuration

19 = (2, 8, 8, 1)

Electrons in K shell (1st) = 2

Electrons in L shell (2nd) = 8

Electrons in M shell (3rd) = 8

Electrons in N shell (4th) = 1

Valence electrons is the number of electrons in the outer shell, i.e. 1 in this atom.

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subject-cta
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