10 electrons because when the amount of electrons is less than the amount of protons, then it is identified as a cation-which means we use the positive sign to represent how many electrons it has lost.
-and remember: anion is when atoms gain electrons (represented by negative sign), whereas cation is when atoms lose electrons (represented by positive sign). I guess this is a very problematic concept to get used to coz sometimes anions can be confused for the positive sign and the cations can be confused for the negative sign.
-I hope this helped or don't hesitate to reply any things i may have missed, or any concepts you would like me to further discuss about.
