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John Dalton presented the idea of atoms in a book, where he invisioned atoms as tiny little balls. For about 100 years this was how people invisioned atoms.
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J. J. Thompson proposed a new idea. He proposed that atoms were just positively charged spheres. Almost looking like a blueberry muffin.
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Scientists used to think that atoms were the smallest piece of matter, which was proved false by Ernest Ruthford. Ruthford discovered that atoms were actually made up of a nucleus, a positively charged center, and electrons, which orbited around the nucleus.
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Ernest Rutherford concluded that the atom is mostly empty. He stated the electrons would float around a small positively charged nucleus.
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Niels Bohr determined that electrons aren't just floating around the nucleus, that they are in layers. Atoms give off and absorb energy when the electrons move from one layer/shell to another.
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In 1932 scientists discovered protons and neutrons. Protons and neutrons make up the nucleus. Protons are positively charged, and neutrons have no charge at all. causing the nucleus to have a positive charge.
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James Chadwick discovered the neutron, a particle with almost the same mass as a proton, but no electrical charge.
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Scientists knew that like charges repelled each other, so how did the nucleus stay together and didn't fly apart? Mesons are the answer. Mesons are small uncharged particles that keep the protons and neutrons together. These became the smallest piece of matter.
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Protons and neutrons were discovered to be made up of smaller particles. These particles are called gluons and quarks. There are different kinds of quarks. There are Up, Down, Strange, Charm, Top, and Bottom. Protons have two Up quarks and one Down quark. Neutrons are made of two Down quarks, and one Up. Quarks are held together by gluons. This is the modern atomic model.
