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Here given, Electrostatic force of repulsion -F = 3.7 × 10-9N Let us say charge is q1 = q2 = q distance between two charges-r = 5 Å = 5 × 10-10 m,To find the number of electrons missing - n = ?Using Coulomb's law, F = 14π ∈0q1 q2r2 ⇒3.7 × 10-9 = 9 × 109 qq(5 × 10-10)2⇒ q2 = 3.7 × 10-9 × 25 × 10-209 × 109 = 10.28 × 10-38 ∴ q = 3.2 × 10-19 coulombAs q = ne∴ n=qe=3.2 × 10-191.6 × 10-19 = 2