The Periodic Table

1. The Periodic Table

2. Atomic Structure Review • Atoms are made of protons, electrons, and neutrons. • Elements are atoms of only one type. • Elements are identified by the atomicnumber (# of protons in nucleus).

3. Energy Levels Review • Electrons are arranged in a region around the nucleus called an electron cloud. Energy levels are located within the cloud. • At least 1 energy level and as many as 7 energy levels exist in atoms.

4. Energy Levels Review • Electrons in levels farther away from the nucleus have more energy. • Inner levels will fill first before outer levels.

5. Energy Levels & Valence Electrons • Energy levels hold a specific amount of electrons: • 1st level = up to 2 • 2nd level = up to 8 • 3rd level = up to 8(first 18 elements only)

6. Energy Levels & Valence Electrons • The electrons in the outermost level are called valence electrons. • Determine reactivity - how elements will react with others to form compounds • Outermost level does not usually fill completely with electrons

7. Dmitri Mendeleev—published the _________ of the periodic table (1869) 1st version • Arranged in order of increasingatomicmass • Left gaps for missing • (or undiscovered) elements • Because of the consistency of elements, Mendeleev predicted the properties of many of the missing elements quite accurately. www.wikipedia.com

8. www.wikipedia.com

9. Henry Moseley—rearrangedMendeleev’s table into the current version • Arranged by atomicnumber (number of protons) • With Moseley’s table, it became clear how many elements were still undiscovered www.wikipedia.com

10. The Modern Periodic Table In the modern periodic table, there are 7rows called periods. A periodis a row of elements in the periodic table whose properties change gradually and predictably. The periodic table also has 18 columns called groups. A group contains elements that have similar physical or chemical properties. A group is also known as a family.

11. The Modern Periodic Table(cont’) The periodic table is divided into two main parts: The RepresentativeElements and The Transition Elements Each element can be classified as a metal, nonmetal, or metalloid.

12. www.fotofects.com www.noble.matthey.com http://www.hardwarewirecloth.com metal- element that: • has luster (reflects light) 2)malleable(can be flattened into sheets) 3) ductile (can be stretched into a wire) 4) good conductors of heat and electricity

13. http://www.dprkorea-trade.com www.uncp.edu www.lowes.com nonmetal—element that is: 1) usually a gas or a brittlesolid 2) poor conductor of heat and electricity metalloid—element that share some properties of both metals and nonmetals. These are sometimes called semimetals.

14. Atomic number 1 H 1.008 Element symbol Atomic mass Symbol—represents the name of the element. Always written with 1st letter capitalized and 2nd letter (if applicable) lower case. Atomic number—represents the number of protons in the nucleus Atomic mass—number of protons plus neutrons. On the periodic table, that is the “relative” mass and is calculated based on the percentage of the different isotopes.

15. Representative Elements—elements in groups 1 & 2, and 13-18or the “A” elements in the periodic table; includes metals, metalloids, and nonmetals

16. www.webelements.com Group 1 or 1A • Called Alkali Metals • Highly reactive in water and combining with other substances • Reactivity gets greater as you go down the table Lithium: found in batteries (esp for camera) Sodium: found in table salt in combination with chloride Potassium: found in bananas,sunflower seeds, and potatoes

17. www.blackpearlbotanicals.com www.amonline.net.au www.wikipedia.com Group 2 or 2A • Called Alkaline Earth Metals • Slightly lessreactive than the alkali metal in the same period. Magnesium: combined to makeEpsom salt Calcium: milk and other dairy products; in your bones

18. www.dentist.net www.newstarget.com Group 17 or 7A • Called Halogen Group • Means “salt formers” • Alkali + Halogen = Salt Fluorine— prevent tooth decay Chlorine— in table salt; kills bacteria in water Bromine— dyes, pesticides,medicines Iodine— disinfectant for wounds; photography; put in table salt for health

19. www.texasphotoplus.com mcst.tec.me.us Group 18 or 8A • Called Noble Gases • Rarely combines with other elements because it has a full outermost shell • ONLY found in nature uncombined Helium— balloons, blimps Neon— signs Ne— red-orange He— yellow Ar— bluish-violet Argon—most abundant Noble gas; protective gas shield for welding, light bulbs, etc. Krypton—used in bulbs to help them burn longer

20. Transition Elements • elements in Groups 3-12or the “B” elements on the periodic table 2) all are metals. 3) Most found combined to form ores

21. Transition Metals • Most have a higher melting point than representative elements • W-Tungsten used in light bulbs; highest boiling point at 3,410 C • Hg-Mercury used in thermometersand barometers

22. Inner Transition Elements Lanthanides • Also called rare earths, because at one time they were thought to be scarce • Soft enough that they can be cut with a knife • Are so similar, they are hard to separate when found together in ores

23. Inner Transition Elements Actinides • Are all radioactive • Most are synthetic • Californium—252 is used to kill cancer cells Synthetic elements can be made using a particle accelerator. Atomic nuclei are caused to collide at high speeds hoping they will fuse together forming new elements. They are called “heavy” elements and usually last only a few seconds before decaying into a lighter element.

24. www.citaexam.com www.gs-titanium.com Transition Elements and Dentistry Dentists used to use amalgam to fill cavities which was made of a mixture of silver, copper, tin, and mercury. Due to concerns with mercury, new resins, composites, and porcelains that are the same color as the tooth have been developed. Orthodontists are now using nickel and titanium alloys for wire braces. These wires have shape memory. When they are heated, they can “remember” their shape and will return to that shape if forced out of it.