Atomic Theory Notes

In class, we learned about Dalton's Atomic Theory and JJ Thomson's, Rutherford's, and the current atomic model. Following are a summary of the notes for each of these model's:

• Dalton's Atomic Theory
• Elements are made of tiny particles called atoms.
• All atoms of a given element are identical.
• The atoms of a given element are different from those of any other element.
• Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers and types of atoms.
• Atoms are indivisible in chemical processes. That is, atoms are not created or destroyed in chemical reactions. A chemical reaction simply changes the way the atoms are grouped together.
• JJ Thomson

• Used a cathode ray tube to show that atoms of any element could be made to give off what we now know as electrons
• He concluded that every atom has these tiny, negative charged particles
• He also knew that atoms have a neutral charge, so there must be an equal amount of positively charged particles  
• Also known as "plum pudding model" or "chocolate chip cookie model"
• No nucleus

• Rutherford

• Shot high velocity alpha particles at an atom expecting there to be very little to deflect the particles
• Some particles bounced back
• Concluded that the only way they could have bounced back was if most of the atom's mass was concentrated in a nucleus
• Eventually discovered that the nucleus contained protons
  
• Current model
• Also known as the "cloud model"
• Electrons move around nucleus in a cloud
• Electron location is pinpointed using proabability