Matter, Atoms, Elements, Compounds, Mixtures, and Isotopes Flashcards
Combined the idea of elements with earlier theories about the Atom. (1803-1805)
John Dalton
What were John Dalton’s four theories of matter and atoms ?
1) matter is made of Atoms
2) Atoms cannot be divided
3) Atoms of the same element are alike
4) different elements are made up of different atoms
Thought of Atoms as a hard sphere that was the same throughout (circle)
John Dalton
Set up experiment using glass tube, electrodes, and wires connected to a battery. Found that when a battery was connected, greenish color glow appeared. Hypothesized that glow was caused by streams of particles.(1870)
William Crookes
Cathode ray tube
Crookes. CRT.
Wanted to test Crookes’ hypothesis to determine if glow was really charged particles or stream of light. He placed a magnet beside the tube from Crookes’ and found that the beam was bent towards the magnet. Light cannot be bent by a magnet so he was able to conclude that the stream was charged particles. Negatively charged particles are now called electrons. He inferred electrons are now part of every kind of atom.(1897)
JJ Thompson
Negatively charged, Thompson
Electrons
Thought an atom was a circle with a bunch of pluses and minuses inside
JJ Thompson
Wanted to prove a Thompson’s theories of the Atom were correct. He set up an experiment in which alpha particles(positive charge) would be aimed at a gold foil. Foil was surrounded by florescence screening that would give a flash each time it was hit by a positive charge. He hypothesized almost all mass of Atoms positive charge was crammed into a small space in the center of the atom.(nucleus) (1906)
Ernest Rutherford
This person’s model either looks like the symbol from Big Bang theory or it could look like a circle with the nucleus in the middle and minuses surrounding it. This just depends on what she has on the test.
Ernest Rutherford
Electrons
Negative charge, Rutherford
Positive charge, protons. The mass of the Atoms were almost 2 times as much of the mass of protons. He concluded there was another component. He found neutrons. (1920)
Ernest Rutherford
Neutrons
Same mass as protons, but electrically neutral, more likely to be close to the nucleus since they are attracted to the positive charge of the protons
Finding neutrons
1) find atomic mass
2) round atomic mass
3) AM rounded- P
Atoms of the same element have different numbers of neutrons, can be written as fractions, not the most common form of an element
Isotopes
