1. Chapter 5 Organizing The Elements

2. OBJECTIVES Describe how Mendeleev arranged the elements in his table
Explain how the predictions Mendeleev made and the discovery of new elements demonstrated the usefulness of his periodic table
Describe the arrangement of elements in the modern periodic table
Explain how the atomic mass of an element is determined and how atomic mass units are defined

3. Identify general properties of metals, nonmetals, and metalloids
Describe how properties of elements change across a period in the periodic table
Relate the number of valence electrons to groups in the periodic table and to properties of elements in those groups
Predict the reactivity of some elements based on their locations within a group
Identify some properties of common A group elements

4. In 1750 scientists had identified only 17 elements most of these were metals
As the number of identified elements grew so did the need for organization
In 1789 Antoine Lavoisier grouped elements according to categories called metals, non-metals, gases and earths

5. In 1860 Mendeleev (Russian) needed to describe the now known 63 elements to his students
On cards, he listed the name, mass and properties of the 63 elements
He arranged them in order of increasing atomic mass. He was able to break the elements into rows (see pg 127 Fig. 3 and columns based on the properties of the elements

6. Columns increased from TOP to BOTTOM
He knew that not all elements were discovered yet so he left room for them
Properties of elements are related to its location in the table
Review questions 1-5 pg. 129

7. 5.2 Modern Periodic law
In the modern periodic table, elements are arranged by increasing ATOMIC NUMBER (number of protons)
PERIODS
Each row in the periodic table is a period
Ex. Period 1 has 2 elements period 2 and 3 have 8 elements
The number of elements in each period varies because of the available orbitals increase from energy level to energy level

8. In other words the first energy level has only 1 orbital so, the 1 electron in a H atom and the 2 electrons in a He atom can fit in this orbital
But Li contains 3 electrons so 2 can fit in the 1st orbital and the other electron has to go in the 2nd orbital(or energy level) this is why Li is the first element in Period 2

9. Na (sodium) the first element in period 3 has one electron in its 3rd orbital or energy level
K (potassium), the first element in Period 4 has one electron in its 4th orbital
This pattern applies to all elements in the first column on the table

10. GROUPS (FAMILIES)
Each COLUMN is called a group or family
The elements within a group have similar properties (electron configurations)
The electron configuration determines the chemical properties
THE PATTERN OF REPEATING CHEMICAL PROPERTIES IS CALLED PERIODIC LAW
REFER TO FIG. 7 PGS

11. Atomic Mass
Copy Fig. 8 into your notebook
There are 4 pieces of information for each element
Name of the element, its symbol, its atomic number, and its atomic mass(the number of isotopes and their mass in nature)
Atoms of 2 isotopes have different atomic masses(isotopes have different # of neutrons than protons) they are usually equal

12. Classes of Elements
Solids, liquids, gases based on their state at room temperature
Symbols solids (black) liquid (purple) gas (red)
Elements are divided into those that occur naturally and those that do not
Ex. Elements with an atomic number of 93 or above DO NOT OCCUR NATURALLY
1-92 occur naturally

13. Third classification is based on general properties
Metals—located on left (blue)
Non-metals located on right (yellow)
Metalloids located in the middle (green)

14. METALS
Majority of elements are metals
Represented by blue boxes
Good conductors of heat
Electric current
Solid at room temperature (except mercury)
Most are malleable
Many are ductile (able to be drawn into thin wire)

15. Groups 3 through 12 are referred to as transition metals
These transition metals form a bridge between the elements on the left and right
One property of these metals is their ability to form compounds with distinct colors
Ex. Tinted glass
They are among the 1st elements discovered

16. NONMETALS
Represented by yellow boxes
Have properties opposite to those of metals
Poor conductivity of heat and electric
Low boiling points
Many are gases at room temperature
Are brittle (will shatter or crumble)

17. METALLOIDS
Represented by green boxes
Properties of these elements fall somewhere between metals and nonmetals
Their ability to conduct heat or electric depends on their temperature

18. Variation across a Period
Changes in the properties of elements change in a similar way when you move from left to right (except for period 1)
From left to right, elements become less metallic and more nonmetallic
Most reactant elements or on the left side of the table
Most reactive nonmetals are on the right side (group 17)
Copy fig. 13 into your notebooks
Complete questions 1-5 and 7

19. Valence electrons
An electron that is in the highest occupied energy level of an atom
Valence electrons play a key role in chemical reactions
The properties of elements vary because the number of valence electrons increases from left to right

20. Remember that elements in a group have similar properties because they have the same number of valence electrons
Ex. Hydrogen and Lithium have I valence electron

21. Alkali metals elements in group 1A
1 valence electron
Highly reactive
Ex. Sodium chloride (table salt)
Group 1A Li, Na, K, Rb, Cs, Fr
Their reactivity increases from TOP TO BOTTOM

22. Alkaline Earth metals
Group 2A
Contain 2 valence electrons
Harder than metals in group 1A
Differences in reactions with water
Calcium and magnesium are essential to biological functions

23. Magnesium
Key role in photosynthesis
Mixture of magnesium and other metals can be as strong as steel but much lighter
Calcium
Keeps bones and teeth strong, toothpastes may contain calcium to polish teeth
Plaster casts contain calcium sulfate

24. The Boron Family
Group 3A
Contain 3 valence electrons
Aluminum(metal) most abundant metal in the earth’s crust
Boron(metalloid)

25. The Carbon Family
Group 4A
4 valence electrons
Contains 1 nonmetal(carbon)
2 metalloids(silicon, germanium)
2 metals(tin, lead)
Life on earth would not exist without carbon, most compounds in your body contain carbon
Silicon is the 2nd most abundant element in the crust

26. The Nitrogen family
Group 5A
Contain 5 valence electrons
Contain 2 nonmetals(arsenic, antimony)
1 metal(bismuth)
1 nonmetal gas (nitrogen)
1 solid nonmetal(phosphorus)
In this group phosphorus and nitrogen are most important
Contained in fertilizers and compounds in your body to release energy

27. The Oxygen family
Group 6A
Contain 6 valence electrons
3 nonmetals (oxygen, sulfur, selenium)
2 metalloids (tellurium, polonium)
Oxygen is the most abundant element in the earth’s crust
Can be stored as a liquid, under pressure
Ozone is another form of oxygen ground level is an eye irritant, in the atmosphere absorbs radiation

28. The Halogens
Group 7A
7 valence electrons
Highly reactive nonmetals
2 gases (fluorine, chlorine)
1 liquid (bromine)
1 solid (iodine)
All react easily with most metals

29. Fluorine compound used to prevent tooth decay, non-stick coatings
Chlorine is in bleach, and used to kill bacteria in drinking water and pools (bromine for hot tubs)
Your body needs iodine to keep your thyroid gland working properly

30. The Noble Gases
Group 8A
8 valence electrons (except helium) (2)
This means these elements have a full outer shell
This group does not react with any other elements
Questions 1-10 page 145
Internet activity—see if you can find the 25 essential elements to the human body and 3 elements that should be avoided completely