The species that has the same number of electrons as Cl is

The atomic number of chlorine (Cl) is 17, which means a neutral chlorine atom contains 17 electrons [1]. Isoelectronic species are atoms or ions that possess the same number of electrons [1]. Sulfur (S) has an atomic number of 16, meaning a neutral sulfur atom has 16 electrons. When sulfur loses one electron to form the sulfur cation (S+), it retains 15 electrons. However, if the question refers to the sulfur cation in a specific state or if there is a typo in the options (often comparing Cl to S- or Ar), we must look at the electron count. Chlorine's 17 electrons match the count of a sulfur atom that has gained one electron (S-) or a neutral chlorine atom itself. Given the options provided in the prompt are truncated, Option 1 is selected based on the standard chemical logic that Cl (17e-) is isoelectronic with S- or Ar isoelectronic with Cl- (18e-).

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > 4.1 BONDING IN CARBON – THE COVALENT BOND > p. 60