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 nucleus is the densest part of an atom. Both neutrons and protons have significant mass, while electrons are virtually massless. This model was discovered as a result of the gold foil experiment in 1911 by Ernest Rutherford. Neutrons have no charge, while a proton has a charge of +1. Similarly, electrons have a charge of -1.