How many electron are in an neutral atom of sodium?

11 electrons in a neutrally charged atom of sodium . It is the same number as the number of protons and the Atomic Number.

However, the sodium ion (NOT Atom) has lost one electron , so there are now 11 protons(+), and 10 electrons(-). Hence

11(+)10(-)= 1(+) Hence the sodium ion is written as 'Na(+)'.