1. The Periodic Table
5.3 and 5.4

2. Development of the Periodic Table
The periodic table was created by a Russian scientist named Dmitri Mendeleev.
He arranged the elements in order of increasing atomic mass.
He noticed properties repeated in a pattern.

3. He made several predictions about properties of yet to be discovered elements, which turned out to be correct.

4. 5.3 Modern Periodic Table
Is arranged according to increasing atomic number. (discovery of the proton allowed for this change)
Shows the name, symbol, atomic number and atomic mass number of the element.
Lists only the atoms of elements that are stable.

5. Additional Info Atoms which gain or lose neutrons are called isotopes
Atoms which gain or lose electrons are called ions

6. Classes of Elements
Most elements in the periodic table are metals. They are found on the left side and center of the table. Non-metals are found on the right side.
Some elements act a little like metals and a little like non-metals. They are called metalloid. Silicon is a metalloid.

7. Each column in the periodic table is called a group or family
Each column in the periodic table is called a group or family. There are 18 groups. Elements in the same group have similar properties.
A horizontal row is called a period. They are numbered 1 to 7.

8. Alkali Metals Column 1 Extremely reactive
Only appear in nature as compounds
Outer orbits have one extra electron (They like to combine with elements that will take their extra electron)
Example: Lithium, Sodium, Potassium

9. Alkaline Earth Metals Column 2
Very reactive, but not as much as Alkali
Outer orbits have two extra electrons (They like to combine with elements that will take their 2 extra electrons)
Example: Magnesium, Calcium

10. Transition Metals Belong to Groups 3 to 12
make up most of the metals you know: gold, silver, copper and tin

11. Non Metals Are Groups 13 to 18
Have families called: Boron family, Carbon family, Nitrogen family, Chalcogens (Oxygen family), Halogens (Fluorine family) and Noble Gases

12. Halogens Column 17 Very reactive Usually appear in compounds
Outer orbits need one electron to complete them. (They like to combine with elements that can give them another electron.)
Example: Fluorine, Chlorine, Iodine

13. Noble Gases Column 18 (far right hand side) All gases
Outer orbits are filled
They are inert meaning they do not react with other elements (They have all the electrons that they need)
Example: Helium, Neon, Argon, Xenon

14. Hydrogen In its own group 1 proton, no neutrons 1 electron
a gas, colourless, tasteless, odourless
highly flammable
usually appears in compounds
likes to react with alkali metals to gain an electron
likes to react with halogens to lose an electron

15. Periods horizontal rows in the periodic table
first period has 2 elements, H & He
the second period has 8 elements
the third period has 8 elements
the atomic number increases from left to right

16. 5.4 Trends in the Periodic Table
Remember that elements are arranged according to increasing atomic number
Properties of elements were found to be determined by the electron arrangement
Atoms in the same group have the same number of electrons in their outer energy level, and thus, react in the same way.

17. Filling the Outer Energy Levels
The goal of an atom is to fill its outer orbit.
In a chemical reaction, one atom can join with another atom by: gaining, losing or sharing valence electrons.
Valence electrons – number of electrons in the outermost energy level

18. a. Reactivity and Valence
Atoms that have a full set of valence electrons (8e) are chemically stable and don’t react easily with other atoms. (Noble gases)
Atoms other than noble gases become stable by transferring/sharing electrons
The closer an element is to the noble gases, the more reactive the element is.

19. Helium is the only noble gas that doesn’t have 8 valence electrons
It acts as a noble gas because it has a full outermost energy level (2e-)

20. Example What is the valence of Fluorine? (check your Bohr diagram) 7e-
What does it have to do to fill its outermost energy level: lose, gain or share electrons?
Gain 1 electron
7 valence e- + 1 e- = 8e-

21. Example What is the valence of Sodium? 1e-
What does it need to do to fill its outermost energy level? Gain, lose or share?
Lose 1e- (because it takes more energy to gain 7e- than to lose 1e- to make 8 outermost e-)

22. The previous 2 examples show how atoms react with other atoms according to their valence electrons.
The resulting particles become either a negative or positive ion (gains or loses e-)

23. b. Reactivity and Atom Size
The distance from the centre of the nucleus to the outermost electrons determines the size of an atom.
Atomic size increases down a group and across a period.
The farther the valence electrons are, the more easily they can be lost, thus, are more reactive.

25. Homework Read Section 5.3 Do Page 206 #1-6 and Read Section 5.4
Do pg 211 # 2, 3, 5, 6, 7