Atomic Structure : this animation shows a semi-classical view of an atom with a central solid nucleus and orbiting electrons. The electrons are shown as yellow spheres that are attracted to the dense nucleus. In "reality", electrons in atoms are more like standing waves but the old planetary model does have some uses (it is easier to visualize for a start). The nucleus, which consists of protons (shown in red) and neutrons (shown in grey) is shown with its particles heaving and moving.
URANIUM is a very heavy radioactive metallic element. It contains 92 protons (hence atomic number = 92) and 92 electrons. The number of neutrons varies and so several isotopes are found. The nucleus is rather unstable and can split (nuclear fission).The roiling particles in the animation give the impression that the nucleus is only just holding together. Uranium is important in nuclear power reactors and has been used in atomic bombs.