An electron in the 3s orbital. The order of electron orbital energy levels starting from lowest to highest is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p.
        
                    
             
        
        
        
Answer:
6
Explanation:
p orbital can hold up to six electron. Argon electron configuration will be 1s²2s²2p⁶3s²3p⁶
 
        
                    
             
        
        
        
Fluorine 20 (F - Atomic number 9 and atomic mass 20). Firstly we need to know what is beta decay. Beta decay occurs when one neutron changes into a proton and an electron therefore the atomic mass will remain the same as even though we loose a neutron it is replaced by a proton, the atomic number is always raised by 1 when one beta decay occurs. The produced electron is shot out of the nucleus at an incredible speed. This speedy electron we call a beta particle.
Ok now the reaction.
 20       20        0
F  -> Ne    +     e
 9         10       -1
Remember the atomic number determines the nature of the element ( i.e what elemnt it is).
Hope this helps :).