Which element does not form a stable ion with the same electronic structure as argon? A aluminium
B chlorine
C phosphorus
D potassium

the answer is A, but i chose D. i just need to know why is it wrong. thanks!

The number to the right of an element's symbol (ex. c-12) identifies the of an isotope.

If a molecule with a molecular formula of c13h18 is treated with an excess of h2 in the presence of finally divided pt metal under conditions required for maximum hydrogenation of the molecule to give a molecule with a formula c13h24, how many rings are in the molecule?

Word equation for k+ h2o yield koh + h2