1. Periodic Table, Part 2 (Chapter 5)
Unit 3
Periodic Table, Part 2
(Chapter 5)

2. 5.1 Organizing the Elements
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.

3. The Search for Order
Until 1750, scientists had identified only 17 elements. These elements were mainly metals such as copper and iron. The rate of discovery increased rapidly as chemists began to investigate materials in a systematic way. As the number of known elements increased, so did the need for a way to organize them.

4. In 1789, Antoine Lavoisier grouped the known elements into categories he called metals, nonmetals, gases, and earths.
For the next 80 years, scientists looked for different ways to classify the elements; but none of them worked for all of them.
In the 1860s, Dmitri Mendeleev, a Russian chemist, would discover such a principle.

5. While playing his favorite card game (a version of solitaire), Mendeleev developed a way to best organize the now known 63 elements.
His strategy involved lining up the elements in rows in order of increasing mass, paying close attention to how each element reacted with oxygen and hydrogen. Soon a pattern emerged….similar properties began to show up in the columns.

6. Mendeleev had developed what is now known as a periodic table-an arrangement of elements in columns based on a set of properties that repeat from row to row.
Mendeleev could not create a complete table as many elements had not yet been discovered so he had to leave spaces for these elements.
Mendeleev was not the first to arrange elements in a periodic table or the first to leave spaces for missing elements. He was, however, able to offer the best explanation for how the properties of each element were related to its location on the table.

7. Evidence:
Mendeleev gave names to the missing elements after elements in the same group. He could predict the type (metal, nonmetal….), the melting points, the densities, etc… based upon the location on the periodic table.
1875: Galium
1879: Scandium
1886: Germanium
Chemists could now not only predict properties of new elements, they could explain the chemical behavior of different groups of elements.

8. Dmitri Mendeleev Video

9. 5.2 The Modern Periodic Table
Objectives:
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.
Identify general properties of metals, nonmetals, and metalloids.
Describe how properties of elements change across a period in the periodic table.

10. The Periodic Law
In the modern periodic table, elements are arranged by increasing atomic number (number of protons).
Periods: Each row of the periodic table. As the periods increase, so do the number of orbitals/energy levels.

11. Groups: Each column on the periodic table
Groups: Each column on the periodic table. The elements within each group have similar chemical properties and similar electron configurations.
This pattern of repeating chemical properties is the periodic law.

12. The Element Atomic Number Symbol Element Name Atomic Mass
A value that depends on the distribution of an element’s isotopes in nature and the masses of those isotopes.
Element Name
Atomic Mass

13. Atomic Mass
In order to have a convenient way to compare the masses of atoms, scientists chose one isotope to serve as a standard.
Scientists assigned 12 atomic mass units to the carbon-12 atom which has 6 protons and 6 neutrons.
An atomic mass unit is defined as one twelfth the mass of a carbon-12 atom.
The atomic masses of elements on the periodic table are weighted averages of all isotopes of that element.

14. Classes of Elements Elements are classified in three different ways:
Solids, Liquids, Gases (at room temperature)
Naturally Occurring (1-92) v. Created (93+)
Metals (left), Nonmetals (right), Metalloids (middle)

15. Metals Majority of the elements .
Good conductors of electric current and heat.
Except for mercury, solids at room temperature.
Most are malleable.
Many are ductile (can be pulled into wires)
Some are extremely reactive while others are not.
Metals on the left side of the periodic table are the most reactive.
Transition Metals-form a bridge between elements on the left side of the table with those on the right.
Unique property-form compounds with distinctive colors.

16. Metals/Transition Metals Videos

17. Nonmetals Poor conductors of electric current and heat.
Low boiling points cause many to be gases at room temperature.
Some are extremely reactive while others do not react at all. Others fall in between.
Most reactive is Fluorine.
Nonmetals are most reactive on the right side of the periodic table.

18. Nonmetals Video

19. Metalloids
Elements with properties that fall between metals and nonmetals.
Ability to conduct electric current varies with temperature.
Only 8 elements:
Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), Polonium (Po), and Astatine (At)

20. Metalloids Video

22. 5.3 Representative Groups
Elements in a group have similar properties because they have the same number of valence electrons.
Valence Electron: an electron that is in the highest occupied energy level of an atom. These electrons play a key role in chemical reactions. Properties vary across a period because the number of valence electrons increases from left to right.

23. Alkali Metals Group 1A One valence electron
Extremely reactive-so much so, they only exist as compounds in nature.
Reactivity increases from the top of the group to the bottom.
Includes: Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr)

24. Sodium: Hard as cold butter Can be cut with a sharp knife
Melts at 98°C
Lower density than water
Reacts violently with water; must be stored in oil.

25. Alkaline Earth Metals Group 2A Two valence electrons
Harder metals than 1A
Differences in reactivity related to the ways the elements react with water.
Includes: Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra)

26. Magnesium:
Key role in the process to produce sugar in plants.
Often used in the frames of bicycles and backpacks.
Calcium:
Needed to keep bones and teeth strong.
Calcium carbonate-main ingredient in chalk, limestone, coral, and pearl.
Calcium sulfate-main ingredient in casts.

27. The Boron Family Group 3A Three valence electrons
Includes: Boron (B), Aluminum (Al), Gallium (Ga), Indium (In), and Thallium (Tl).

28. Boron, Silicon, and Oxygen: Boron:
Aluminum:
Most abundant metal in Earth’s crust. It is less reactive than Na and Mg, strong, lightweight, malleable, and a good conductor of electric current.
Used in packaging, window screens, window frames, and gutters.
Used to make parts for cars and airplanes.
Boron, Silicon, and Oxygen:
Used to make glass that does not shatter easily.
Boron:
Used to make laboratory glassware and cookware.

29. The Carbon Family Group 4A Four valence electrons
Includes: Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn), and Lead (Pb)
Becomes more metallic as you move down the column.

30. Carbon: Silicon: Found in most of the compounds in the human body.
The second most abundant element in Earth’s crust.
Silicon dioxide-quartz rocks, sand, and glass.
Silicates-found in clay used to make pottery.
Silicon carbide, used to tip saw blades to make them last longer.

31. The Nitrogen Family Group 5A Five valence electrons
Includes: Nitrogen (N), Phosphorus (P), Arsenic (As), Antimony (Sb), and Bismuth (Bi)
Nitrogen and phosphorus are the two most important elements in this group.

32. Nitrogen: Phosphorus: Used in fertilizers
Combined with phosphorus in the human body-used to control reactions and release energy in food.
Phosphorus:
White phosphorus is so reactive it bursts into flames when it is in contact with oxygen.
Red phosphorus is used to make matches ignite.

33. The Oxygen Family Group 6A Six valence electrons
Includes: Oxygen (O), Sulfur (S), Selenium (Se), Tellurium (Te), and Polonium (Po)

34. Oxygen: Sulfur: Most abundant element in Earth’s crust.
Needed to sustain life.
Allows flammable materials to burn.
Ozone-absorbs harmful radiation emitted by the sun. Found in the atmosphere.
Sulfur:
One of the first elements to be discovered because it is found in large natural deposits.
Main function is the production of sulfuric acid.

35. Halogens Group 7A Seven valence electrons Highly reactive nonmetals
Easily reacts with most metals.
Includes: Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At)

36. Fluorine: Chlorine: Iodine: Compound used to prevent tooth decay.
Used to make nonstick coatings for pans.
Chlorine:
Used to kill bacteria in drinking water and swimming pools.
Iodine:
Used in your body to keep your thyroid gland working properly. This gland controls the speed at which reactions occur in your body.

37. Noble Gases
Group 8A
With the exception of Helium, which has two valence electrons, all other noble gases have eight valence electrons.
Colorless and odorless
Includes: Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rd)

38. Argon:
Used in some light bulbs-increases the number of hours the bulb can be lit before it burns out.
All noble gases except radon are used in “neon” lights.

39. Essential Elements
There are 25 essential elements to the human body which are generally ingested as part of compounds found in food.
Major Elements
Lesser Elements
Trace Elements
Hydrogen, oxygen, carbon, nitrogen, phosphorus, calcium
Iron, potassium, zinc, sodium, sulfur, chlorine, magnesium
Vanadium, chromium, molybdenum, manganese, cobalt, copper, boron, tin, silicon, selenium, fluorine, iodine
Account for almost 90 percent of your body mass.
Help your body build tissues and maintain other cell processes.
Perform important functions-red blood cells would not mature without cobalt.

40. Harmful Elements Lead: Mercury: Arsenic:
Too much can lead to organ damage and learning difficulties, especially in young children.
Mercury:
Toxic and can damage the brain and nervous system.
Arsenic:
Poisonous.

41. Too Much of a Good Thing Zinc: Found in almost every cell of the body.
Helps to support a healthy immune system.
Too much can cause anemia by reducing iron uptake.
Sodium:
Needed to maintain water balance and nerve function.
Too much can cause high blood pressure.
Selenium:
Needed to maintain a healthy immune system.
Too much can cause nerve damage.