The species that has the same number of electrons as 3517Cl is
A) 3216S: Atomic number 16. Neutral Sulfur has 16 electrons.
B) 3416S+: Atomic number 16. Neutral Sulfur has 16 electrons. S⁺ means it lost 1 electron (16 – 1 = 15 electrons).
C) 4018Ar+: Atomic number 18. Neutral Argon has 18 electrons. Ar⁺ means it lost 1 electron (18 – 1 = 17 electrons).
D) 3516S2-: Atomic number 16. Neutral Sulfur has 16 electrons. S²⁻ means it gained 2 electrons (16 + 2 = 18 electrons).
Therefore, 4018Ar+ has 17 electrons, the same number as neutral 3517Cl. These species are isoelectronic.