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400 BCE
Aristotle
Aristotle believed that a mass of incomprehensible size was everywhere around us. -
400 BCE
Democritus
Democritus was the first person to name the atom. He called it atomus. It means indivisible in Greek. He believed that once you divided matter to it’s smallest form, it was an atom. There was nothing smaller than that. -
John Dalton
John Dalton’s model was known as the Solid Sphere Model. He discovered that elements are made up of the same atoms that all have the same mass. For example, oxygen has the same type of atoms. -
Dmitri Mendeleev
Dmitri Mendeleev developed the first periodic table that was organized by atomic mass. -
JJ Thomson
JJ Thomson’s model was known as the Plum Pudding Model. He believed that an atom was a positively charged sphere with electrons spread evenly throughout (like raisins in a plum pudding). -
Ernest Rutherford
Ernest Rutherford’s model is known as the Nuclear Model. He discovered than an atom is mostly made up of empty space. He also found that the mass of the atom is mainly made up from the protons in the center of the atom. -
Henry Moseley
Henry Moseley discovered that the number of protons is different in each element, so that’s why their atomic number is different. -
Niels Bohr
Niel’s Bohr’s model was known as the Bohr Model. He discovered the electron and how it orbits and jumps between different energy levels. -
Schrodinger and Heisenberg
Erwin Schrodinger and Werner Heisenberg created the Electron Cloud Model. He discovered that electrons orbit on different levels.
