3. C. Chemical symbols
B. Relative masses and charges of proton, neutron
and electron
A. Structure of atom
D. Electronic configuration
Recap on Atomic Structure
4. C. Chemical symbols
B. Relative masses and charges of proton, neutron
and electron
A. Structure of atom
D. Electronic configuration
Recap on Atomic Structure
6. WHAT IS AN ATOM?
Atoms are the smallest particle of an element.
7. WHAT IS AN ELEMENT?
•An element is a ____ substance that cannot be
_____up into 2 or more simpler substances by
chemical processes.
pure
spilt
8. The Story of Atoms
Ernest
Rutherford
(1871 -1937)
Democritus
460 BC
Sir James
Chadwick
(1891 -1974)
1898
Joseph John
Thompson
(1856-1940)
Atoms have positive
charges concentrated in
their small nucleus!
There are
neutrons!
PLUM
PUDDING
MODEL
Niels Bohr
(1885-1962)
9. Bohr’s Atom
electrons in orbits
nucleus
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/atom.swf
10. Structure of Atom
10
An atom consists
mostly of empty
space.
Negatively
charged
electrons move
around the
nucleus in fixed
orbits or paths.
A positively
charged nucleus,
densely
concentrated in
the centre.
The nucleus
contains protons
and neutrons,
which are tightly
packed.
11. C. Chemical symbols
B. Relative masses and charges of proton,
neutron and electron
A. Structure of atom
D. Electronic configuration
Recap on Atomic Structure
12. C. Chemical symbols
B. Relative masses and charges of proton,
neutron and electron
A. Structure of atom
D. Electronic configuration
Recap on Atomic Structure
13. Relative Charges & Relative Masses Of
Protons, Neutrons & Electrons
Sub-atomic
particles
Symbol Relative
mass
Relative
charge
*Proton p 1 +1
*Neutron n 1 0
*Electron e 1/1840 -1
•When No. of proton = no. of electrons in an atom
•It is electrically neutral
•It has no net charge.
14. C. Chemical symbols
B. Relative masses and charges of proton, neutron
and electron
A. Structure of atom
D. Electronic configuration
Recap on Atomic Structure
15. C. Chemical symbols
B. Relative masses and charges of proton, neutron
and electron
A. Structure of atom
D. Electronic configuration
Recap on Atomic Structure
16. 16
O
16
8
chemical symbol
mass number
(nucleon number)
proton number
(atomic number)
P=E
No. of
protons= no.
of electrons
atomic number (proton number) is the number of
protons in an atom.
Each oxygen atom has 8 protons.
As the number of electrons is equal to the number of
protons in an atom, each oxygen atom contains 8
electrons.
Mass=P+N
mass number is the total number
of protons and neutrons in an
atom.
Number of neutrons in the
oxygen atom is: 16 – 8 = 8.
Interpreting Chemical Symbol
17. C. Chemical symbols
B. Relative masses and charges of proton, neutron
and electron
A. Structure of atom
D. Electronic configuration
Recap on Atomic Structure
18. C. Chemical symbols
B. Relative masses and charges of proton, neutron
and electron
A. Structure of atom
D. Electronic configuration
Recap on Atomic Structure
21. Summary for Atomic Structure (I)
• The structure of an atom
• The relative charges & relative masses of
proton, neutron & electron
• Defined mass number & atomic number
• Learnt how to interpret chemical symbols
• The electronic configuration of atoms
