Respuesta :
Metals : Since metals have tendency to lose extra electrons in their valence shell and attain neutrality.
Non-metals : Since metals have tendency to gain extra electrons in their valence shell and attain neutrality.
Lower : Since lower elements can easily lose electrons from the valence shell because of weak attraction from the nucleus.
Higher : Since higher elements can not easily lose electrons from the valence shell because of strong attraction from the nucleus.
intermediate