1. The Periodic Table

2. Why is the Periodic Table important? The periodic table is the most useful tool to a chemist. You get to use it on every test. The periodic table organizes the elements in a particular way. A great deal of information about an element can be gathered from its position in the period table. You can predict with reasonably good accuracy the physical and chemical properties of the element. You can also predict what other elements a particular element will react with chemically.

3. Elements Science has come along way since Aristotle’s theory of Air, Water, Fire, and Earth. Scientists have identified 90 naturally occurring elements, and created about 28 others.

4. The most abundant element in the earth’s crust is oxygen.

5. Pre-Periodic Table Chemistry … Working with chemistry began with the early manipulation of fire. 8000 years ago it was found that when certain rocks were heated, melted metals poured out and when cooled could be worked into useful tools. 5000 years ago it was found that by mixing tin with other metals changed its properties allowing for harder more durable tools Copper + Tin Bronze - - - - - Bronze age

6. Pre-Periodic Table Chemistry … As time passed, more and more elements were discovered as the alchemists searched and experimented with new techniques for isolating and combining elements. Up to the late 1700’s, most discoveries were based on chance but as new techniques were devised and chemists began to recognize patterns, develop theories and make predictions about undiscovered elements, there was a rapid increase in the number of known elements.

7. Pre-Periodic Table Chemistry … Until the early 1800’s, there was no organization of elements, and chemistry didn’t make sense. Eventually similar properties were noticed among different groups which led to simple categorization.

8. Pre-Periodic Table Chemistry … The Metals From the Greek word metallon meaning “mine”, metals make up 75% of the known elements. Properties: Good conductors of heat and electricity Maleable Ductile High density High boiling points Lustrous Gold – soft, maleable, does not tarnish Silver – reactive, used in photography Copper – very good conductor Iron – Very hard, used in construction Aluminum – Tarnishes easily Mercury – liquid at room temperature

9. Pre-Periodic Table Chemistry … The Metalloids Show properties of both metals and nonmetals and are good semiconductors Boron - an essential plant nutrient and can be toxic in high concentrations Silicon - the most abundant metalloid and is used for microchips, glass, cement and ceramic production Arsenic - a well known poison used in pesticides and herbicides and is also used to make alloys harder

10. Pre-Periodic Table Chemistry … The Nonmetals Properties: No lustre Poor conductors of heat and electricity Most are solid or gas Bromine – the only nonmetal that is liquid at room temperature Fluorine – the most reactive element Selenium – used in glass making and pigments and is an essential nutrient

11. Pre-Periodic Table Chemistry … In 1817 Johann Wolfgang Dobereiner noticed that the chemical properties of Sr was closely related to the properties of Ca and Ba. He called this grouping a triad. A distinctive feature of a triad was that of the atomic mass. When elements were arranged in order of their increasing atomic mass, the atomic mass of the middle element was approximately the arithmetic mean of the other two elements of the triad. Several other triads were created based on his system but eventually there were not enough triads to make the system useful.

12. Pre-Periodic Table Chemistry … In 1863, John Newlands suggested that elements be arranged in “octaves” because he noticed (after arranging the elements in order of increasing atomic mass) that certain properties repeated every 8th element. His theory was rejected by the Chemical Society as it failed beyond the element Calcium.

13. Dmitri Mendeleev: Father of the Table In 1869, Dmitri Mendeléev created the first accepted version of the periodic table. He grouped elements according to their atomic mass, and put elements in columns by the way they reacted. By doing this found that the families had similar chemical properties. Blank spaces were left open to add the new elements he predicted would occur.

14. Dmitri Mendeleev: Father of the Table Mendeleev's elements (1869) compared to periodic "Groups."

15. In spite of Mendeleev’s great achievement, problems arose when new elements were discovered and more accurate atomic weights determined. By looking at our modern periodic table, can you identify what problems might have caused chemists a headache? Dmitri Mendeleev: Father of the Table Ar & K Co & Ni Te & I Th & Pa

16. The Current Periodic Table In 1913, through work with X-rays, Henry Mosley determined the actual nuclear charge (atomic number) of the elements. He rearranged the elements in order of increasing atomic number. Mendeleev wasn’t too far off. Now the elements are put in rows by increasing ATOMIC NUMBER. The horizontal rows are called periods. The vertical columns are called groups or families.

17. Periodic Law When elements are arranged in order of increasing atomic number there is a periodic pattern in their physical and chemical properties.

18. The History Continues There were very few discoveries between the late 1800’s and the mid 1900’s until Nuclear technology provided a technique that led to more.

19. Groups…Here’s Where the Periodic Table Gets Useful!! Elements in the same group have similar chemical and physical properties!! Why?? They have the same number of valence electrons. They will form the same kinds of ions and therefore react in similar ways.

20. The families - Hydrogen Hydrogen belongs to a family of its own. Hydrogen is a diatomic, reactive gas. Hydrogen was involved in the explosion of the Hindenberg. Hydrogen is promising as an alternative fuel source for automobiles

21. The families - Alkali Metals 1 st column on the periodic table (Group 1) not including hydrogen. Exhibit metallic properties and are highly reactive including reacting vigorously with water. Always combined with something else in nature to form a salt. Low density, low melting point and good conductors. Soft enough to cut with a butter knife.

22. The families - Alkaline Earth Metals Second column on the periodic table. (Group 2) Reactive metals that are always combined with nonmetals in nature. Harder than group 1 metals Have a gray-white lustre Several of these elements are important mineral nutrients such as Mg and Ca

23. The families - Transition Metals Less reactive, harder metals Includes metals used in jewelry, construction, plumbing, electric wires, etc.

24. The families - Carbon Family Elements in group 14 Contains elements important to life and computers. Carbon is the basis for the entire branch of organic chemistry. Silicon and Germanium are important semiconductors.

25. The families - Nitrogen Family Nitrogen makes up over ¾ of the atmosphere. Nitrogen and phosphorus are both essential to living things, yet most of the world’s nitrogen is not available to living things as it is in the air and decomposing matter on the Earth’s surface. The red stuff on the tip of matches is phosphorus.

26. The families - Oxygen Family Oxygen is necessary for cellular respiration and is therefore essential for life. Many things with a strong odour contain sulfur

27. The families - Halogens Very reactive, volatile, diatomic, nonmetals Always found combined with other element in nature. Used as disinfectants and to strengthen teeth.

28. The families - The Noble Gases Least reactive of the elements monatomic gases Used in bulbs for sun lamps and fluorescent lighting. Used in between panes of glass Used in blimps. Have a full valence shell.