1. ATOMIC STRUCTURE
S.MORRIS 2006

2. Learning Outcomes Define atom and element
Get an idea of the size of an atom
Basic structure of the atom
Types, numbers of, and properties of subatomic particles in an atom

3. LecturePLUS Timberlake
Atomic Theory
Atoms are building blocks of elements = Atom is the smallest particle of matter that can exist by itself
Similar atoms in each element
Different from atoms of other elements
Two or more different atoms bond in simple ratios to form compounds
LecturePLUS Timberlake

4. HISTORY OF THE ATOM ATOMS John Dalton 1808
suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity and called them
ATOMS

5. HISTORY OF THE ATOM ELECTRON Joseph John Thompson 1898
found that atoms could sometimes eject a far smaller negative particle which he called an
ELECTRON

6. HISTORY OF THE ATOM PLUM PUDDING MODEL 1904
Thompson develops the idea that an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron's charge
like plums surrounded by pudding.
PLUM PUDDING
MODEL

7. HISTORY OF THE ATOM Ernest Rutherford 1910
oversaw Geiger and Marsden carrying out his famous experiment.
they fired Helium nuclei at a piece of gold foil which was only a few atoms thick.
they found that although most of them passed through. About 1 in 10,000 hit

8. HISTORY OF THE ATOM
gold foil
helium nuclei
helium nuclei
They found that while most of the helium nuclei passed through the foil, a small number were deflected and, to their surprise, some helium nuclei bounced straight back.

9. HISTORY OF THE ATOM However, this was not the end of the story.
Rutherford’s new evidence allowed him to propose a more detailed model with a central nucleus.
He suggested that the positive charge was all in a central nucleus. With this holding the electrons in place by electrical attraction
However, this was not the end of the story.

10. HISTORY OF THE ATOM Niels Bohr 1913
studied under Rutherford at the Victoria University in Manchester.
Bohr refined Rutherford's idea by adding that the electrons were in orbits. Rather like planets orbiting the sun. With each orbit only able to contain a set number of electrons.

11. Bohr’s Atom
electrons in orbits
nucleus

12. Structure of the atom
Nucleus
Electrons orbiting the nucleus

13. HELIUM ATOM + - + - Shell proton neutron electron
What do these particles consist of?

14. ATOMIC STRUCTURE
Particle
Charge
Mass
proton
+ ve charge 1
neutron
No charge 1
electron
-ve charge
nil

15. Location of Subatomic Particles
10-13 cm
electrons
protons
neutrons
10-8 cm
nucleus
LecturePLUS Timberlake

16. LecturePLUS Timberlake
Atomic Number
Counts the number of
protons
in an atom
LecturePLUS Timberlake

17. LecturePLUS Timberlake
Periodic Table
Represents physical and chemical behaviour of elements
Arranges elements by increasing atomic number
Repeats similar properties in columns known as chemical families or groups
LecturePLUS Timberlake

18. LecturePLUS Timberlake
Periodic Table 11 Na
LecturePLUS Timberlake

19. Atomic Number on the Periodic Table11 Na
Atomic Number
Symbol
LecturePLUS Timberlake

20. All atoms of an element have the same number of protons11 Na
11 protons
Sodium
LecturePLUS Timberlake

21. LecturePLUS Timberlake
Learning Check AT 1
State the number of protons for atoms of each of the following:
A. Nitrogen
1) 5 protons 2) 7 protons 3) 14 protons
B. Sulfur
1) 32 protons 2) 16 protons 3) 6 protons
C. Barium
1) 137 protons 2) 81 protons 3) 56 protons
LecturePLUS Timberlake

22. LecturePLUS Timberlake
Solution AT 1
State the number of protons for atoms of each of the following:
A. Nitrogen
2) 7 protons
B. Sulfur
2) 16 protons
C. Barium
3) 56 protons
LecturePLUS Timberlake

23. LecturePLUS Timberlake
Number of Electrons
An atom is neutral
The net charge is zero
Number of protons = Number of electrons
Atomic number = Number of electrons
LecturePLUS Timberlake

24. LecturePLUS Timberlake
Mass Number
Counts the number of
protons and neutrons
in an atom
LecturePLUS Timberlake

25. LecturePLUS Timberlake
Atomic Symbols
Show the mass number and atomic number
Give the symbol of the element
mass number
23 Na sodium-23
atomic number 11
LecturePLUS Timberlake

26. LecturePLUS Timberlake
More Atomic Symbols
O P Zn
p+ p p+
n n n
e- e e-
LecturePLUS Timberlake

27. Learning Objectives Bohr Structure Electronic Configuration
Drawing structure of atoms

28. ATOMIC STRUCTURE
Electrons are arranged in Energy Levels or Shells around the nucleus of an atom.
first shell a maximum of 2 electrons
second shell a maximum of 8 electrons
third shell a maximum of 8 electrons

29. 1. Electronic Configuration
ATOMIC STRUCTURE
There are two ways to represent the atomic structure of an element or compound;
1. Electronic Configuration
2. Dot & Cross Diagrams

30. ELECTRONIC CONFIGURATION
With electronic configuration elements are represented numerically by the number of electrons in their shells and number of shells. For example;
Nitrogen
configuration = 2 , 5 7
2 in 1st shell
5 in 2nd shell N
= 7 14

31. ELECTRONIC CONFIGURATION
Write the electronic configuration for the following elements; 20 11 8 Na O Ca a) b) c) 16 23 40
2,8,8,2
2,8,1
2,6 17 14 5 Cl Si B d) e) f) 11 35 28
2,8,7
2,8,4
2,3

32. N DOT & CROSS DIAGRAMS Nitrogen
With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example; X
Nitrogen N 7 X X N X X 14 X X

33. DOT & CROSS DIAGRAMS O Cl
Draw the Dot & Cross diagrams for the following elements; X 8 17 X O Cl a) b) X 35 X 16 X X X X X Cl X X X X X X X O X X X X X X X X X X

34. SUMMARY The Atomic Number of an atom = number of
protons in the nucleus.
The Atomic Mass of an atom = number of
Protons + Neutrons in the nucleus.
The number of Protons = Number of Electrons.
Electrons orbit the nucleus in shells.
Each shell can only carry a set number of electrons.

35. When an atom loses an electron it gets a positive charge
When an atom loses an electron it gets a positive charge. When an atom gains an electron it gets a negative charge.

36. How many neutrons and electrons are there in the ion
45 Sc +3 21