1. The periodic Table, the atom and Bohr Diagrams
Lesson 2
August 25th, 2010

2. Grade 9’s
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3. Elements and the Periodic Table
Elements are pure substances that consist of atoms. The periodic table consists of over 100 elements all of which have a certain spot on the periodic table.

4. Important Features of the Table
The elements are also organized in two fashions horizontal vertical and horizontal lines called groups and periods.
Groups- elements with similar chemical properties in a vertical column in the main part of the table;
Period – elements, arranged in a horizontal row, whose properties change from metallic on the left to non-metallic on the right

5. Metals- left side of the periodic table
The majority of elements on the periodic table are metals. All metals, except for mercury are solids at room temperature. Metals have the following properties.
Malleable
Lustre
Ductile
Conductors

6. Non-Metals – Right side of the periodic table
Most of the remaining elements in the periodic table are non-metals
Non-metals generally have these properties:
Non-conductor of electricity in its solid form
At room temperature most are gasses or solids
Solids are brittle and lack the lustre of metals

7. Metalloids- middle right of the periodic table
Some elements do not fit as metals or non-metals.
These fit on either side of the staircase that divides the metals and the non-metals. They have some properties of metals and some properties of non- metals.

8. Group Names Alkali Metals: First group in the periodic table.
Soft, Silvery coloured solids.
React violently with water.
Most reactive metal family

9. Group Names Alkaline earth metals: Second group in the periodic table.
Light
React violently

10. Group Names
Transition metals: Theses metals have a wide variety of properties and reactivates.
Hard,
Strong
Conduct electricity

11. Group Names Representative elements: Groups 1,2 and 13-17.
Metals and non-metals
All states of matter found
Follow periodic law.

12. Group Names Halogens: Non-metals in group 17.
Solids, liquids and gases
Extremely reactive.

13. Group Names Noble gasses: Gasses at room temperature. Low MP and BP
Un-reactive

14. Elements and Atomic Structure
Atoms are composed of three subatomic particles
Protons- Heavy positively charged particle found in the nucleus
Neutrons -are neutral particles that have the same mass as protons and are located in the nucleus
Electrons- Negatively charged particles with almost no mass. They circle the nucleus at different energy levels.

16. The atomic number (Z) refers to the number of protons that are located in the nucleus of the atom. This number also provides the elements placement on the periodic table. If the atom is electronically neutral it will also contain the same number of electrons.
( x number of (+ive) protons + x number of ( -ive) electrons = 0 Charge

17. The Atomic Mass (A) refers to the number of protons and neutrons in the nucleus of the atom.
The Number of neutrons can be found by using the formula N = A – Z

18. Example:
Oxygen has an atomic number of 8 and a atomic mass of 16.00
N = A – Z
N = – 8 = 8 neutrons

19. Bohr Diagrams
To represent electron arrangements at various orbits we use Bohr diagrams. Each orbit has a set number of electrons.

20. Orbit #
# of Electrons 1 2 8 3 4 18

21. Every row in the period contains a shell
Every row in the period contains a shell. The farther you move down the table the more shells you added to the diagram. H = 1 shell, Li = 2 shells, K = 3 shells.
Moving left to right on the periodic table adds valence electrons to the shells of that row. Na has 1 valence e-, Mg has 2 valence e-, Al has 3 valence e-, etc.

22. Drawing Bohr Diagrams Examples Draw the Bohr diagram of Hydrogen
N = A – Z
N =
Draw the Bohr diagram of Helium
Draw the Bohr diagram of Lithium
Draw the Bohr diagram of Beryllium
Draw the Bohr diagram of Aluminum
Draw the Bohr diagram of Argon