What is the correct electron configuration for a ground-state atom with 7 electrons?

d: the voltage of the secondary coil is less than that of the primary coil.

im not suree sorry if wrong

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.