3 Elements in the Periodic Table are arranged in order of their proton number. a Define the meaning of the term proton number.
b Argon, proton number 18, has a larger mass number than potassium, proton number 19. Explain why this .
d An atom of which element has only two of the three particles listed in the table above?
e Argon and helium are both noble gases. In what way are their electron structures similar? ​