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.