The document summarizes the history and development of atomic theory from ancient Greek philosophers to modern atomic structure. It discusses early atomic models proposed by philosophers like Democritus and scientists like Dalton, Thomson, and Rutherford. It then explains atomic structure including subatomic particles like protons, neutrons, and electrons. The periodic table is introduced as a way to organize the elements based on their atomic structure and properties. Key periodic table terms like atomic number, mass number, groups, and periods are defined.

1. Atomic Theory

2. Greek Philosophers
• Aristotle
4Elements of matter
-Earth
-Fire
-Air
-Water

3. Democritus
Matter is made of atoms (cannot be further divided), the word atom
comes from the Greek word “atomos” which means indivisible.

4. • Atoms were tiny particles that could not be divided
• John Dalton proposed that an atom is a sphere of
matter that is the same throughout and can’t be seen
by human eyes
• Marble Model

5. • Came up with the idea of the electron negatively charged particle
• Thomson discovered that all atoms contain electrons, which are tiny,
negatively charged particles. Thomson proposed that an atom is a
sphere of positive charge. The electrons are mixed uniformly in the
sphere.
• Cookie Model

6. Ernest Rutherford
• He hypothesized that almost all the mass and all the
positive charge of an atom is concentrated in an extremely
tiny nucleus at the center of the atom.

7. • Thought electrons traveled in fixed paths around the
nucleus called energy levels.

8. Atomic Structure
• Arrangement and number of sub-atomic particles
•Protons
•Neutrons
• Electrons

9. • Center or core of an atom
• Contains 99.9% of the weight of an atom
• Contains protons and neutrons

10. • Positively Charged Sub-atomic particles
• Found in the nucleus
• All protons are a like

11. • Neutrally charged (no charge) sub-atomic particle
• Found in nucleus

12. • They are the negatively charged particles orbiting the
nucleus.
• It is much smaller than the protons and the neutrons .

13. What is the net charge of
the atom ?
• The atom is formed of positively charged proton in the
nucleus and negatively charged electrons in the energy
level ,but they are equal to each other in number ,making
the net charge of the atom “neutral”.
No of positive protons = No of negative electrons

14. • They are charged atoms
• Number of positive protons = Number of negative electrons.
Positive
ion
Negative
ion

15. If the atom lost an electron ,therefore the number of positive protons
are more than the negative electrons making the atom positively
charged
Positive Ion

16. If the atom gained an electron ,therefore the number of negative
electrons
are more than the positive protons making the atom negatively
charged
Negative Ion

17. • Atomic number is the number of Protons in an atom
• All atoms of a particular element have the SAME number of protons (All
Carbon atoms have 6 protons)
• In a neutral atom,
The atomic number =The number of electrons

18. • Also called atomic weight or Mass Number
• Sum weight of protons and neutrons in an atom

19. Calculate the mass number of each of
the following atoms

20. O
8
16
Atomic
number
Mass
number
Symbol
Name Oxygen
Atomic number= Number of protons= Number of electrons
Mass number= Number of protons + Number of neutrons

21. Calculating Neutrons:
• Mass number = protons + neutrons
so…..
• Neutrons = mass number – protons
What is the number of neutrons of the following atom ?
A
45
21

22. Developing a Periodic Table
• In 1869 Dimitri Mendeleev was working on a way to
classify elements.
•At the time, more than 60 elements had been
discovered.
• And he arranged the elements according to their
atomic mass

23. 100 table The periodic table is
a chart of the
elements arranged
according to their
atomic number in
rows and columns
according to their
physical and chemical
properties.

26. Symbol

27. What is the periodic table?
•The periodic table is a chart of the elements
arranged into rows and columns according to
their physical and chemical properties.
• It can be used to determine the relationships
among the elements.

28. Groups and Periods
- Columns in the periodic table represents “groups”
- There are 18 groups in the periodic table.
- Elements of the same the same group have the same
chemical properties as the all have the same number of
electron/s in the outer most energy levels.

29. - Rows in the periodic table represent “periods”.
- There are 7 periods in the periodic table .
- Elements of the same period have the same number
of energy levels

30. The Periodic Table of Elements

31. Periodic Table
A great deal of information about an element can be gathered from
its position on the period table.
Understanding the organization and plan of the periodic table will
help you obtain basic information about each of the 118 known
elements.

32. Mass Number
Atomic Mass (Mass Number) is the number
…………….
__________
Atom p+ n0 e- Mass #
___ ___ ___ ___
Oxygen - 8
- 33 42
______ ___ ___ ___
- 31 15
______ ___ ___ ___

33. Recall - How are P, N, e- related?
• atomic number = # protons
• # protons = …………….
• # protons + # neutrons = atomic mass
# neutrons = …………….
…………….

34. • How many protons, neutrons and electrons are found in
an atom of Cs?
• _____________
• …………….
• …………….
• Therefore, # Neutrons = …………….
_____________
_____________
55
Cs
133
Example 1

35. 11
Na
Sodium
23
___________
___________
___________

36. Example 2
 If an element :Magnesium
a) number of protons
b) number of neutrons
c) number of electrons
d) complete symbol
=_____________
= _____________
= _____________
_____________

37. Periodic Table

38. Metals

39. Properties of Metals
Metals appear to the left of the dark ziz-zag line on
the periodic table. Most metals are solid at room
temperature.

40. Properties of Metals
Metals have luster.
This means they are
shiny

41. Properties of Metals
Ductile
metals can be drawn
into wire.

42. Properties of Metals
Malleable
metals can be
hammered
into sheets

43. Properties of Metals
Metals have a high melting point. They are
also very dense.

44. Properties of Metals
Conductors
Metals are
good
conductors of
electricity and
heat

45. Nonmetals

46. Elements
Substance that contains only one kind of atom

47. Compounds
-Are substances made of atoms of two or more elements
that are chemically combined.
-The chemical formula of a compound shows the elements
that are in it
-Example:
SiO₂ (sand): It is formed of 1 Silicon atom
2 oxygen atoms

48. -Compounds don’t have the same properties of the
elements forming them
Example:
The ordinary table salt is a compound called NaCl
It is formed of :
1 atom of Sodium and 1 atom of chlorine
Where “Sodium” is a metal

49. • And “Chlorine” is a gas
But when they combine together they give a product of
different properties which is the table salt

50. How compounds are formed ?
-Compounds hold together because atoms bond or
attach to one another

51. How atoms can attach or bond with
each other?
They either
Share
electrons
Gain
Or
lose
electrons