Which of the following are isoelectronic species i.e, those having the same number of electrons?
`Na^(+),K^+, Mg^(+), Ca^(2+), S^(2-), Ar`

Explanation

To determine which of the given species are isoelectronic (i.e., have the same number of electrons), we will calculate the number of electrons for each species.

### Step-by-Step Solution:

1. **Calculate the number of electrons in Na⁺ (Sodium ion)**:
- Atomic number of Na = 11
- Na⁺ has lost 1 electron.
- Number of electrons = Atomic number - Charge = 11 - 1 = **10 electrons**.
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