Question

exam 1: atomic theory/structure
which best describes the current (quantum) atomic theory?
atoms consist of electrons circling in definite orbits around a positive nucleus.
an atoms mass is determined by the mass of its neutrons.
atoms are composed of electrons in a cloud around a positive nucleus.
atoms can easily be split, at which time they become radioactive.

Explanation:

In quantum atomic theory, electrons are in a probability - cloud around the nucleus.

Answer:

Atoms are composed of electrons in a cloud around a positive nucleus.