Choose the statement that is true. a) outer electrons efficiently shield one another from nuclear charge. b) core electrons effectively shield outer electrons from nuclear charge. c) valence electrons are most difficult of all electrons to remove. d) core electrons are the easiest of all electrons to remove. e) all of the above are true.

The statement that is true is as follow:

B) Core electrons effectively shield outer electrons from nuclear charge.

Explanation:

Effective Nuclear Charge:

It is defined as the net positive nuclear charge of the protons which is exerted  on the valence electrons.

The option a is incorrect as outer electrons don't shield each other from nuclear charge but the inner electrons do this.The option b is correct as the core electrons effectively shield outer electrons from nuclear charge of protons.The option c is incorrect as the valence electrons are not the difficult rather they are the easiest electrons to remove.The option d is incorrect as the core electrons are the difficult of all electrons to remove as you have to remove the valence electrons first.The option e is incorrect as all above are not true except one that is option b.