Which element has twice as many electrons in its second shell as in its first shell?

Which elements has a total of three shells, with four electrons in its valence shell?

Which elements has a total of two shells, with three electrons in its valence shell?

Name two elements that have two electrons in their outermost shells.

What elements has the electronic configuration 2, 8,2?

Name three elements that have a single electron in their outermost shells.

Which halogen has the highest electron gain enthalpy and which halogen has the highest Electronegativity?

Can a particle has zero velocity while its acceleration is uniform ?