1. Periodic Table
Chapter 5

2. Organizing the elements
Section 1

3. Let’s Review! Chemical properties
Any property that can only be tested by changing the chemical make-up of the substance.
Physical properties
Any property that can be tested without changing the chemical make-up of the substance
Atomic mass
Mass of protons and neutrons
Atomic number
Unique to each element, same as number of protons

4. Dmitri Mendeleev 1870, there were 63 elements known to man
He organized them in order of their atomic mass, and saw a pattern from their properties.
Was working on this while Thomson and Rutherford were still “exploring” the atom

5. Dmitri Mendeleev
Arranged his table with repeating properties in columns, starting a new row each time the chemical properties repeated
Left blank spaces in his table, concluding that these spaces were elements that hadn’t been discovered yet.
Based on the patterns and the other elements around the blank space, he predicted the properties of those elements

6. What he called ekasilicon – it was discovered a few years later
An Example
What he called ekasilicon – it was discovered a few years later
Prediction
Atomic Mass
72 amu
Density
5.5 g/mL
Appearance
dark gray metal
Melting Point
high melting point
Germanium
72.6 amu
5.3 g/mL
gray metal
937o C

7. Mendeleev’s Table

8. Dmitri mendeleev Some problems arose…
A few elements appeared to be slightly out of place
Mendeleev put them in the right place and said their atomic masses were incorrectly measured
However, he was actually arranging them by the wrong number

9. Henry Moseley ~1910: Discovered atomic number
He rearranged the periodic table by this number and it fell into perfect order
Mendeleev’s table worked because as the number of protons increase, the atomic mass should increase, however if there are fewer neutrons it could decrease

10. Periodic Law
Periodic Law: physical and chemical properties of the elements are periodic functions of their atomic numbers
In other words, when the elements are arranged by their atomic numbers, you should see chemical and physical properties repeating themselves

11. Rows Left to right – called periods
Elements in the same periods show a pattern
As you move left to right, conductivity and reactivity change, and elements become less metallic

12. Columns Top to bottom – called groups
Elements in a group have similar chemical properties
The elements in the same group (column) have the same number of valence electrons

13. Exploring the periodic table
Section 2

14. The periodic table is organized by atomic number
Remember
The periodic table is organized by atomic number
For a neutral atom, the number of protons equals the number of electrons

15. Valence Electrons
The trends found in a periodic table are a result of electron arrangement, specifically, the number of valence electrons
Valence Electron: electrons in the outermost shell

16. Valence Electrons
The group number of an element will tell you the number of valence electrons it has
Group 1 elements: 1 valence electron
Group 2 elements: 2 valence e- ’s
Skip the middle
Group 13 elements: 3 valence e- ’s
Groups elements: 4, 5, 6, 7, and 8 valence e- ’s respectively.

18. Why do we care about electrons?

19. Ion A neutral, stable atom will have equal protons and electrons
When an atom gains/loses electron(s), the atom is no longer neutral and has a charge
It becomes an ion
Ion: a charged atom

20. Ion Ionization: When atoms EITHER gain or lose electrons
All atoms want to have 8 valence electrons in the outer shell – this would make their outer shell full
Elements that are really close to having 8 electrons, desperately want to get there, and tend to be the most reactive.
Elements that are already “full” are considered inert, they don’t react because they don’t need to gain or lose electrons

21. Let’s Recall Protons = positive charge Electrons = negative charge
p+ # CANNOT change, but e- # can
So…
If an atom GAINED electrons, would they be more positive, or more negative?
If they LOST electrons?

22. Cation Remember…group 1 elements have 1 electron in their outer shell
So…group 1 elements like to give up their single electron
This would make it more POSITIVE
We call this a cation

23. Anion
Remember…elements in group 17 have 7 electrons in its valence shell (it would like 8)
So…it will accept an electron from a “donor”
This would make it more NEGATIVE
We call this an anion

24. Let’s Practice Group 16 Give Up? or Gain? Group 13 Give Up? or Gain?

25. Charges How do we know if an atom is an ion?
We show it with an exponent
Cations have a +, and anions have a –
If an atom has gained 3 electrons
It is more negative = Al3-
If an atom has lost 3 electrons
It is more positive = Al3+

26. The Periodic Table It is divided into three major categories Metals
Nonmetals
Metalloids (semiconductors)
These categories are based on general properties and are further broken down into families

27. Metals are left of the “staircase”
Nonmetals are to the right
Metalloids share properties of both

28. Metals Most elements are metals
Like to give up their valence electrons
Physical properties
high luster (shiny), conductive (heat and electricity), malleable (bendable), ductile (stretchable), high density, high melting point
All except Hg are solids at room temperature
Chemical properties
Most will react with oxygen

29. Nonmetals Like to gain electrons Physical properties
dull, don’t conduct, brittle, low density, low melting points
Like ashes (mainly carbon)
Can be solid, liquid or gas at room temperature depending on the element.

30. Metalloids (Semiconductors)
Share properties of both metals and nonmetals
Can be shiny or dull, conduct ok, ductile and malleable or brittle
These elements have become really important because of the computer revolution
Computer chips are made out of semiconductors (normally Si)
By position Al is a metalloid, but its properties make it a light metal

31. Families of elements
Section 3

32. Families Families of elements have similar properties
Each family also has the same number of valence electrons

33. Alkali Metals, Alkaline-Earth Metals, Transition Metals

34. Alkali Metals Group 1 (excluding H) 1 valence e-
Very reactive, especially with water
Soft, shiny white metals (can be cut with a knife!)
Low density (Li, Na, and K float in water)

35. Hydrogen
Hydrogen is in group 1 but is not an alkali metal, because it is only 1 proton and 1 electron (no neutrons)
Its properties are closer to a nonmetals than to a metal
it is a colorless, odorless, explosive gas with oxygen

36. Alkaline-Earth Metals
Group 2
2 valence e- ’s
Silver colored, more dense metals
Not as reactive as alkali metals, but still very reactive metals.
Magnesium is used in flash bulbs

37. Transition Metals Groups 3-12 1 or 2 valence e- ’s
Most are silver in color
Somewhat reactive
These are most metals you are familiar with
iron, gold, copper, zinc and nickel
Since they are not that reactive they have more everyday uses.

38. Transition Metals
Two bottom rows are the Lanthanide and Actinide series, sometimes called innertransition metals
Lanthanide: also called rare- earth metals
Actinide: very radioactive and not easily found in nature

39. Nonmetals
Halogens, Noble Gases

40. Halogens Group 17/7a 7 valence e- ’s
All nonmetals (can be solid, liquid or gas)
Extremely reactive with alkali metals
Chlorine is added to water as a disinfectant.
The “chlorine” added to pools is a compound containing Chlorine, by itself chlorine is a green gas

41. Noble Gases Group 18/8a 8 valence e- ’s (except Helium)
Full outer shell of electrons
All are gases
Extremely non-reactive (inert)
All found in the atmosphere
“Neon” lights contain a variety of Noble Gases

42. Other Nonmetals and Metalloids
Groups contain both nonmetals and metalloids
Nonmetals: Oxygen, Nitrogen, Carbon, Sulfur, Phosphorus, and Selenium
Metalloids: Boron, Silicon, Germanium, Arsenic Antimony, and Terellium
The group is named by the first element in the column

43. Boron Group Group 13 3 valence e- ’s
1 metalloid, all others are metals
All are solids at room temperature
Aluminum is the most common
it is actually the most abundant element on the planet.

44. Carbon Group Group 14 4 valence e- ’s
1 nonmetal, 2 metalloids, 2 metals
all are solids
Pure carbon can be diamonds, soot (ashes) or graphite.
Silicon and germanium are used for computer chips
Tin and lead are common metals

45. Nitrogen Group Group 15 5 valence e- ’s
2 nonmetals, 2 metalloids, 1 metal
All but nitrogen are solids
Nitrogen makes up 78% of the air
Phosphorus is in several compounds (soaps)
Arsenic is a well known poison

46. Oxygen Group Group 16 6 valence e- ’s 3 nonmetals, 2 metalloids
except oxygen, all are solid
Oxygen makes up 21% of the air
it is necessary for things to burn
sulfur is a yellow rock, that can burn.