in the pn junction of a diode when a pentavalent dopant emits an electron why do we say it has become a positive ion..i mean the dopant is now in its octet state..then why do we call it a cation?

Question

festinger · Answer

Having octet is the very reason why we call it an ion!

For sodium, it loses 1 electron to gain this octet configuration, but now it has 1 more proton than electrons around it, and thus it is positively charged.

anonymous · Answer

because the dopant atom is lacking 1 electron and +ve charge of its nucleus isn't fully compensated by its electrons. So the whole atom is +vely charged. So it is cation.

kainui · Answer

An electron is negatively charged. Since it has the same number of electrons and protons, the charge cancels out to be 0, meaning it's not an ion at all. 

When it loses an electron, it has left the proton's positive charge behind unbalanced. The reason it wants a complete octet has to do with the stability of orbitals based on quantum mechanical principles, NOT on electromagnetism.