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Structure of an Atom Cheat Sheet (DRAFT) by

for students of grade 9

This is a draft cheat sheet. It is a work in progress and is not finished yet.

CHARAC­TER­ISTICS OF SUB-ATOMIC PARTICLEES

PROPERTY
ELECTRON
PROTON
NEUTRON
DISCOVERY
JJ Thomson
E Goldstein
Chadwick
ABSOLUTE MASS
9×10-31kg
1.6×10-27kg
1.6×10-27kg
RELATIVE MASS
1/1840u
1u
1u
CHARGE
negative
positive
no charge
ABSOLUTE CHARGE
-1.6×10 −19
+1.6×10 −19
0
LOCATION
outside nucleus
inside nucleus
inside nucleus

THOMSON'S MODEL

limita­tions of JJ's model of an atom?
couldn't explain stability of an atom, neutron & nucleus. acc. to him, mass of atom was uniformly distri­buted but mass is concen­trated in the nucleus. results of experi­ments by scientists couldn't be explained by this model.
explain his model.
an atom consists of a +vely charged sphere and e- are embedded in it. -ve & +ve charges are equal in magnitude, so the atom is electr­ically neutral.

RUTHER­FORD'S MODEL

any particle in a circular orbit would undergo acc.. during accn, charged particles would radiate energy. thus, revolving electrons would lose energy and fall into the nucleus. thus the atoms would be highly unstable but they're not.
radius of nucleus is about 105 times less than the radius of the atom.

BOHR'S MODEL

only certain special orbits known as discrete orbits of e-, are allowed inside atom. while revolving, e- don't radiate energy. these energy shells are repres­ented by letters K,L,M,N.. or numbers n=1,2,­3,4..

ATOMIC & MASS NUMBER

atomic number = total Np OR Ne
ex; Na: 11, Np OR Ne = 11
mass number = Np+Nn [neuclons]
average atomic mass = mass no.×pe­rce­nta­ge+mass no.×pe­rce­ntage

ISOTOPES /\ ISOBARS

atoms of the same element having same atomic numbers but different mass numbers
atoms of different elements with different atomic numbers but same mass numbers
have same chemical properties but different physical properties
have different chemical properties but same physical properties
ex; 12
6
C 14
6
C
ex; 40
20
Co 40
18
Ar
isotope of: uranium- fuel in nuclear reactors; cobalt- treatment of cancer; iodine- treatment of goitre.
  

ELEMENTS & NEUTRONS

1. H: 0
7. N: 7
13. Al: 14
2. He: 2
8. O: 8
14. Si: 14
3. Li: 4
9. F: 10
15. P: 16
4. Be: 5
10. Ne: 10
16. S: 16
5. B: 6
11. Na: 12
17. Cl: 18
6. C: 6
12. Mg: 12
18. Ar: 22

SYMBOLS OF IONS

Sodium
Na+
Potassium
K+
Silver
Ag+
Copper [I]
Cu+
 
Magnesium
Mg2+
Calcium
Ca2+
Zinc
Zn2+
Iron [II]
Fe2+
Copper [II]
Cu2+
 
Aluminium
Al3+
Iron [III]
Fe3+

SYMBOLS OF IONS [non-m­etallic elements]

Hydrogen
H+
Hydride
H-
Chloride
Cl-
Bromide
Br-
Iodide
I-
 
Oxide
O2-
Sulphide
S2-
 
Nitride
N3-

SYMBOLS OF IONS [polya­tomic ions]

Ammonium
NH
4
+
Hydroxide
OH-
Nitrate
NO
3
-
Hydrogen Carbonate
HCO
3
-
 
Carbonate
CO
3
2-
Sulphite
SO
3
2-
Sulphate
SO
4
2-
 
Phosphate
PO
4
3-