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19 protons and 20 neutrons.  It has 19 electrons in the atom.

So, electron distribution in the shells and sub shells is :

         1s²  2s² 2p⁶  3s² 3p⁶  4s¹
Since there is one electron in the valency shell, its valency is 1. It loses the single electron and forms a positive ion with single charge.    E⁺ or  E+.