1. The Periodic Table

2. Organization
Group/family = vertical column
Period = row

3. Grouping of elements Metals – most elements on the table, left side
Nonmetals – far right and hydrogen
Metalloids – along zig-zag line; divides metals and non-metals

4. Metals Good conductors of heat/electricity Malleable (can be formed)
Ductile (made into wires)
Reflects light
High densities
High melting points
Most are solids at room temperature
Easily lose electrons
corrode

5. Nonmetals Not good conductors of heat/electricity Dull Brittle
Low melting points
Low densities
Are solids, liquids and gasses at room temperature
Tend to gain electrons

6. Metalloids Cross between metals and nonmetals
Solids at room temperature
Can be shiny or dull
Malleable
Ductile
So-so conductors (better than nonmetals, but not as good as metals)
Form semiconductors when bonded

7. Groups/families Group 1 – alkali metals
React with water to form alkalines (bases)
Very reactive; not found alone in nature, found as compounds
Very soft metals
Have one valence (outermost) electron

8. Groups/families Group 2 – alkaline earth metals
Also form alkalines with water
Also very reactive, so not found as pure elements in nature
Not as reactive as group 1
Have 2 valence electrons

9. Groups/families Group 17 – halogens Means “salt former”
Tend to form salts with group 1 elements
Most reactive of the nonmetals
Have 7 valence electrons

10. Groups/families Group 18 – noble gases Very unreactive
All are gases at room temperature
Have a full set of valence electrons
Full set = 8, except for helium which has 2

11. Groups Groups 3 – 12: Transition metals
Can put more than 8 electrons in their outermost orbital
Can use the 2 most outer orbitals to bond (the others use only the outermost)
Can form ions with different charges

12. Development of the periodic table
In 1865, John Newlands, an English Chemist, arranged the elements according to their properties and in order of increasing atomic mass.
He noticed a pattern that repeated every 8 elements, so he called it the law of octaves

13. Development of the periodic table (cont)
Dimitri Mendeleev, in 1869, used this information and produced the first orderly arrangement of all 63 known elements.
He arranged them in a similar way to Newlands and created the first periodic table.
Mendeleev started a new row each time he noticed that the chemical properties of the elements repeated.
He left gaps where he thought newly discovered elements should go and made predictions about these elements

14. Mendeleev’s table

15. Mendeleev’s predicted elements

16. Modern Periodic Table
Elements did not always fit neatly on the table in order of atomic mass
Henry Moseley studied the x-ray spectra of 38 different elements
He noticed a pattern as the atomic mass increased
However, after further study, he realized that the correlation was to atomic number and not atomic mass.
The table was arranged in increasing atomic number and any discrepancies from Mendeelev’s table disappeared

17. Modern Periodic Table (cont)
Periodic Law: the principle of chemical periodicity.
When elements are arranged according to their atomic numbers, elements with similar properties appear at regular intervals.
This law works because of the pattern in the electron configuration of the elements.
Elements in each column of the periodic table have the same number of valence electrons (electrons in their outer energy level)

18. Valence electrons Electron located in the outermost energy levels
Valence electrons are the ones that participate in chemical reactions.
Elements with the same number of valence electrons tend to react in similar ways.
This allows scientists to predict the properties and behavior of unknown elements.

19. Periodic trends
Tells you how certain characteristics change as you move across and down the periodic table
3 trends that we will look at:
Atomic radius
Ionization energy
electronegativity

20. Atomic radius The “size” of the atom
Decreases as you move from left to right across a row
Reason: as you move across a period, you add electrons to the atom in the same energy level. You also add protons to the nucleus, thus increasing the pull of the nucleus on the electrons, drawing them closer to the nucleus (effective nuclear charge)
Increases as you move down a column
Reason being is that when adding electrons, you add them in increasing energy levels, making the atom larger

23. Ionization energy The energy needed to remove an electron from an atom
Increases as you move across
Reason: effective nuclear charge increases requiring more energy to take them away (the outermost electrons are the first ones to be removed)
Decreases as you move down
Reason: the electrons that are added to increasing energy levels are further away from the nucleus, thus the attraction is decreased making it easier to take them away
Also, you have “electron shielding” which is when the inner electrons “shield” the outer ones from the pull of the nucleus

25. Electronegativity An atom’s desire to attract electrons
The more electronegative atom will take electrons away from a less electronegative atom (like a big brother takes toys from the little brother)
Increases as you move across
Reason: effective nuclear charge increases so electrons are attracted more strongly
Decreases as you move down
Reason: electron shielding decreases effective nuclear charge, decreasing the attraction

28. Natural Elements
Only 93 of the elements on the periodic table occur in nature
Technetium (Tc) and Promethium (Pm) were detected in the stars, but not found on earth
Some elements can form through nuclear reactions (fusing of nuclei)
Center of stars
transmutations

29. Transmutations
One element changes into another through a nuclear reaction – NOT ALCHEMY
Radioactive elements do this naturally
We have “created” synthetic elements using particle accelerators
cyclotron

30. Cyclotrons
Speeds particles up to very high energies and then collides them
Nuclei of the particles fuse, creating “new” elements
Some of these are “superheavy” elements
Atomic number greater than 106
Usually only a few nuclei are created, making it hard for scientists to study
They usually decay within a fraction of a second

31. Cyclotron at Berne, Switzerland

32. Cyclotron