The Atom

1
The Atom

• A Brief History

2
The Atom

• Atoms are too small to see directly
• Hard to experiment on something that you cant
  see
• As technology gets better, advances are made on
  unraveling the structure of atoms
• Many scientists have contributed to discovering
  to the structure of the atom, we are looking at
  only four

3
John Dalton (1766-1844)

• Said all things are made of atoms
• All atoms of an element are identical
• Atoms not created or destroyed in a chemical
  reaction
• A compound always has the same ratio and kinds of
  atoms

4
J.J. Thomson (1856-1940)

• Discovered electrons in the late 1800s
• Cathode Ray Tube Experiment (see picture)
• Created plum pudding model

5
Albert Einstein

• Proved atoms existed in 1905
• Looked at small grains of pollen bouncing around
  randomly in water

6
Ernest Rutherford (1871-1937)

• Discovered the nucleus in 1909
• Gold Foil Experiment (see picture)
• Tried to prove Thomson was correct, ended up
  disproving Thomson

7
Ernest Rutherford

• Particles called alpha particles shot towards a
  thin piece of gold foil
• If Thomson was correct, particles should bounce
  straight back
• Ended up going straight through (some were
  deflected at many different angles)

8
Niels Bohr

• Hypothesized electrons orbit the nucleus like
  planets orbit the sun
• Model still taught today
• Model is incorrect

9
The Atom

• The Model Today

10
Protons (p)

• Found inside the nucleus
• Have a charge of 1
• Have a mass of 1 amu
• amu- atomic mass unit
• 1 amu 1.67x10-27 g

11
Neutrons (no)

• Found inside the nucleus
• Have a charge of 0
• Have a mass of 1 amu

12
Electrons (e-)

• Found outside the nucleus
• Have a charge of 1
• Have a mass of 0 amu
• 900 electrons about 1 proton

13
The Nucleus

• Atomic Number tells the number of protons and
  electrons
• Eg if atomic number 27 then 27 p and 27 e-
• Atomic Mass total number of protons and
  neutrons in the nucleus (p n0 atomic mass
• Eg if atomic mass 11 and atomic number 5,
  then 5 p and 6 n0