What is the entire universe
made up of?
The periodic table of elements
Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg ? ? ? ? ? ? ?
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Na Mg Al Si P S Cl Ar
Li Be B C N O F Ne
H He
How do we know?
John Dalton (1766–1844)
An English chemist who revived the ancient Greek’s idea of matter and proposed:
“All matter is made up of atoms. Atoms are the smallest particles of matter and cannot be broken down into smaller units”
Joseph Thomson (1856–1940)
A British physicist who discovered and experimented with cathode rays. It was found that these rays consisted of what are later called electrons by Thomson.
“An atom is a ball of positive charge with electrons dotted evenly through it like currants in a plum pudding. Overall, the atom is neutral”
The “Plum Pudding” Model
Ernest Rutherford (1871-1937)
This New Zealand physicist attempted to prove Thomson’s model of the atom was correct and designed an experiment. However…
The “Plum Pudding” Model
Only a few atoms thick Gold foil
Tiny, positive alpha particles
Screen
They expected the alpha particles to pass straight through the atom… but
about 1 in 8000 got deflected by a large angle (some even got knocked back) – HOW?
Rutherford’s Gold Foil Experiment
James Chadwick (1891-1974)
In 1932, he performed an experiment to discover the third type of sub-atomic particle that is not deflected by an electric or magnetic field – the “neutron”.
Atomic Structure today (or yesterday)
Protons and neutrons are called nucleons.Nucleus is very small compare to the size of the whole atom but has 99.95% of the mass.Electrons move around the nucleus in an unknown way.
Nucleus is made up of protons and neutrons which are bound together by nuclear force.