What do they look like? Tree swallows are small birds (about 14 cm long) with long wings and small legs and feet. They are irridescent greenish-blue on their head, shoulders and back, and white their chin, breast and belly. Tree swallows have a short black beak and dark brownish feet.
Ernest Rutherford concluded that an atom contains a very small, dense center, called a nucleus, with a positive charge as a result of his gold foil experiment.
The first is the tiny atomic nucleus, which is in the center of the atom and contains positively charged particles called protons and neutral, uncharged, particles called neutrons. The second, much larger, region of the atom is a âcloudâ of electrons, negatively charged particles that orbit around the nucleus.