The three subatomic particles

1. Electron
Neutron
Proton

3. In 1838, Michael Faraday passed current through the
glass tube filled with rarefied air. Conducting the
experiment he noticed a strange light arc with its
beginning at the anode (the positive electrode) and
its end almost at the cathode (the negative
electrode). The only place where there was no
luminescence was just in front of the cathode. The
place is called "cathode dark space", "Faraday dark
space", or "Crookes dark space". That was the
beginning of the long and "turbulent" time of
researches on that luminescence. And the
luminescence is called "cathode rays".
MICHAEL FARADAY

5. In this experiment, Faraday showed
that the mass of elements was
proportional to the quantity of
electricity that passed through
them.
2. George J. Stoney- he was a
scientist who first suggested the
term “ Electron” to refer to a
negatively charged particle.

6. 3. Joseph John Thomson-was credited for
his discovery of the first subatomic particle
through his work with the discharge tube.

8. 4. Robert A. Millikan- independently
measured the electrons charge through his
OIL-DROP Experiment. He successfully
attempted to detect and measure the
effect of an individual subatomic particle.

11. Using an atomizer, Millikan sprayed
tiny droplets of oil which passed
between two charged plates. Given a
negative charge(-) by the electrons
released from gas particles by x-rays,
the oil particles were attracted toward
the positive plate. He observed the
speed of the droplets as they moved
toward the positive plates. The
smallest possible charge on a droplet
was taken as the charge of an
individual atom.

12. The quantity is considered to be the basic unit
charge and is given a value of one minus (1-)

13. When the electron was
discovered , the scientists
searched for the positively
charged particles.
1.Eugene Goldstein-

14. Goldstein observed rays passing
through the hole of a cathode in the
cathode tube. These rays are made up
of positive particles. Their
characteristics depend on the gas
inside the cathode tube.The lightest
particle was obtained when Hydrogen
gas was used.

15. 1. Sir James Chadwick- discovered
 the neutron in 1932.
 He found out that
 the particle was
 electrically neutral
an and its mass
was
 approximately the
 same as that of the
 proton.

17. Proton
Symbol
Position in atom
Relative charge
Relative mass
Actual mass ( g)
p+
Inside the nucleus
1+
1
1.673x10
-24

18. Neutron
Symbol
Position in atom
Relative charge
Relative mass
Actual mass
n
Inside the nucleus
0
1
1.675x10
-24

19. Electron
Symbol
-
e
Position in atom
Relative charge
Relative mass
Actual mass
moving around the nucleus
-1
0
1840
1
»
9.109x10
-28

20. Atomic structure
e
e
e
e
e- - - - - - - - electron
n (s)
p (s)- - - - - - - - - - - - - - - nucleus

21. Atomic content of an atom
no. of protons = 11
no. of electrons =11
no. of neutrons = 12
12n
11p
-
e11
Na
23
11
Symbol

22. Atomic Content of C
12
6
 no. of protons = 6
 no. of neutrons = 12 - 6
= 6
 no. of electrons = 6
 (An atom is neutral in charge)

23. Atomic Content of :N
14
7
 no. of protons = 7
 no. of electrons = 7
 no. of neutrons = 14 – 7
= 7

24. Atomic Content of C
14
6
 no. of protons = 6
 no. of neutrons = 14 – 6
= 8
 no. of electrons = 6

25. C
14
6
C
12
6
mass number
atomic number
Mass number = no. of p + no. of n
atomic number = no. of protons

26. Isotopes
Name of element : carbon carbon
No. of protons : 6 6
No. of neutrons : 8 6
No. of electrons : 6 6
Isotopes are atoms of same elements which have the same
atomic number but different mass number
C
14
6 C
12
6

27. Isotopes
C
14
6
C
12
6
Burn in air Carbon dioxideCarbon dioxide
Mass 14 units 12 units
Radioactivity Give radiation Does not give
radiation (stable)

28. Extension : Isotopes ( For reference only )
8n
6p
C
14
6
nucleus
g++
-
e
0
1
7n
7p
N
14
7
nucleus
A neutron in a nucleus of breaks into
Electrons and energy are emitted to the surroundings
C
14
.11
-
+ep
Carbon -14 dating

29. Properties of isotopes
 Same chemical properties
 Different physical properties
 e.g. mass
b.p. and m.p.
radioactivity

30. Actual mass VS relative mass
Mass of 1C
12
6
atom kg
26
10993.1
-
´= Or 12
Which one is more convenience?
Standard reference : 1 is equivalent to
kg
C
27
12
6
10661.1
12
1 of mass
-
´=
Relative mass

31. Simplified rule : We regard
Relative mass of 1p = 1
Relative mass of 1n = 1
Relative mass of 1e = very small
= 0

32. Relative mass of isotopes
Si
28
14
Si
29
14 Si
30
14
Relative mass28 29 30
% abundance92% 4.7% 3.1%
Do the three isotopes have the same chemical properties?
Yes

33. It is difficult and not necessary
to separate the isotopes in most
of the reactions. Average
relative mass of silicon is used to
denote the mass of a silicon
atom.
Relative atomic mass of isotopes

34. Relative atomic mass of silicon ( P.5 e.g.1 )
Si
28
14
Si
29
14 Si
30
14
Relative mass
% abundance
28 29 30
92% 4.7% 3.1%
( Relative ) Atomic Mass of silicon
= 28 x 92% + 29 x 4.7% + 30 x 3.1%
= 28.053
= 28.05

35. Ex1. Relative atomic mass of Chlorine
Cl
35
17
Cl
37
17
Relative mass
% abundance
35 37
75.5% 24.5%
Atomic mass of Chlorine = 35 x 75.5% + 37 x 24.5%
= 35.5