Which element is listed with the number of valence electrons and the number of non-valence electrons in one of its atoms in the ground state?

Regents Chemistry Exam August 2025 Question 31

31  Which element is listed with the number of valence electrons and the number of non-valence electrons in one of its atoms in the ground state?

(1)  Sodium has two valence electrons and 11 non-valence electrons.

(2)  Phosphorus has five valence electrons and 10 non-valence electrons.

(3)  Chlorine has seven valence electrons and 17 non-valence electrons.

(4)  Argon has 10 valence electrons and 18 non- valence electrons.

Solution:

Periodic Table on the Reference table lists all elements with their electron configuration. The last number in electron configuration is the number of valence electrons. The rest of electrons listed are non-valence electrons. For example sodium, Na, is 2-8-1. This means sodium has 1 valence electron and 10 nonvalence electrons. Phosphorus, P, has an electron configuration of 2-8-5. It has five valence electrons and 10 non-valence electrons. Choice 2 is the correct answer choice.

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