Which of the following are NOT possible electron configurations?

What is the mass of sodium in 3 moles of sodium chloride

Using a value of ksp = 1.8 x 10-2 for the reaction pbcl2 pb+2(aq) + 2cl -(aq). if the value of ksp was determined to be only 1.2 x 10-2: too much solid has dissolved. additional precipitate is forming. the solution is unsaturated. the ions are now combining to reduce their concentrations.

According to periodic trend, which of the following most likely has the highest ionization energy? kr be ni sc