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7/26/2019 Chemistry Form 6 Sem 1 01
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PRE UNIVERSITYCHEMISTRY
SEMESTER 1
CHAPTER 1 : MATTER
7/26/2019 Chemistry Form 6 Sem 1 01
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1.1 The Atom
1.1.1 Historical development of atomic theory When atom was first discovered by John Dalton
(1808), he claim that atom are the simplest unit in asubstance.
Later, physicist J.J. Thomson (1897) found out thatatom are made up of even smaller particles withnegative charge electron, Daltons theory was beingrejected.
After that, subatom with a positive charge protonwas discovered by Rutherford in the center of theatom.
At the same decade, Neils Bohr discover that
electrons surrounding nucleus similar as planetsurrounding the Sun, and electrons move about in arich electron region called orbital.
Few years later, Chadwick discovered that not only
proton exist in the center of an atom but also a non-charge subatom neutron.
7/26/2019 Chemistry Form 6 Sem 1 01
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Electron
Nucleus
Proton
Neutron
Particle Symbol Mass
(kg)
Relative
Mass
Charge
(C)
RelativeCharge
Proton p or 11H 1.67 x10-27
1 a.m.u +1.6 x10-19
+1
Neutron n or 10n 1.67 x
10-27
1 a.m.u 0 0
Electron e or 0-1e 9.11 x10-31
_1_ amu1834
-1.6 x10-19
-1
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The path of moving protons, electrons and neutrons is deflected by both
electric field and magnetic field
+
electron proton
<
electr
on
proto
n