Answer:
C.
Explanation:
If there are the same number of protons (+) as electrons (-) they will cancel out and make the atom neutral.
 
        
             
        
        
        
Answer:
Explanation:
Threshold frequency = 4.17 x 10¹⁴ Hz .
minimum energy required = hν where h is plank's constant and ν is frequency .
E = 6.6 x 10⁻³⁴ x 4.17 x 10¹⁴ 
= 27.52 x 10⁻²⁰ J . 
wavelength of radiation falling = 245 x 10⁻⁹ m 
Energy of this radiation = hc / λ 
c is velocity of light and  λ  is wavelength of radiation .
= 6.6 x 10⁻³⁴ x 3 x 10⁸ / 245 x 10⁻⁹
= .08081 x 10⁻¹⁷ J 
= 80.81 x 10⁻²⁰ J 
kinetic energy of electrons ejected = energy of falling radiation - threshold energy 
= 80.81 x 10⁻²⁰  - 27.52 x 10⁻²⁰ 
= 53.29 x 10⁻²⁰ J .