Which statement is true about two isotopes of the same element?

they have the same mass number.
they have different numbers of protons.
they have different locations on the periodic table.
they have different numbers of neutrons.

Four objects each with charge +2.0×10−7c are located at the corners of a square whose sides are 2.0 m long. part a what quantities can be determined using this information? check all that apply. the electric force on a charged object placed at the center of the square. the mass of each object. the total electric potential energy of the system consisting of the four charged objects. part b find the electric force on a charged object placed at the center of the square.