Presentation on theme: "Atomic Structure Review Atoms are made of protons, electrons, and neutrons. Elements are atoms of only one type. Elements are identified by the atomic."— Presentation transcript:
Atomic Structure Review Atoms are made of protons, electrons, and neutrons. Elements are atoms of only one type. Elements are identified by the atomic number (# of protons in nucleus).
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.
Energy Levels Review Electrons in levels farther away from the nucleus have more energy. Inner levels will fill first before outer levels.
Energy Levels & Valence Electrons Energy levels hold a specific amount of electrons: –1 st level = up to 2 –2 nd level = up to 8 –3 rd level = up to 8 (first 18 elements only)
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
Dmitri Mendeleev —published the _________ of the periodic table (1869) 1 st version Arranged in order of increasing atomic mass 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
Henry Moseley —rearranged Mendeleev’s table into the current version Arranged by atomic number (number of protons) www.wikipedia.com With Moseley’s table, it became clear how many elements were still undiscovered
The Modern Periodic Table In the modern periodic table, there are 7 rows called periods. A period is 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.
The Modern Periodic Table (cont’) The periodic table is divided into two main parts: The Representative Elements and The Transition Elements Each element can be classified as a metal, nonmetal, or metalloid.
metal - element that: 1) has luster (reflects light) www.fotofects.com 2) malleable (can be flattened into sheets) 3) ductile (can be stretched into a wire) www.noble.matthey.com http://www.hardwarewirecloth.com 4) good conductors of heat and electricity
nonmetal —element that is: 1) usually a gas or a brittle solid http://www.dprkorea-trade.com 2) poor conductor of heat and electricity www.lowes.com www.uncp.edu metalloid —element that share some properties of both metals and nonmetals. These are sometimes called semimetals.
1 H 1.008 Atomic number 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.
Representative Elements —elements in groups 1 & 2, and 13-18 or the “A” elements in the periodic table; includes metals, metalloids, and nonmetals
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 www.webelements.com Lithium: found in batteries (esp for camera) Sodium: found in table salt in combination with chloride Potassium: found in bananas, sunflower seeds, and potatoes
Group 2 or 2A Called Alkaline Earth Metals Magnesium: combined to make Epsom salt www.blackpearlbotanicals.com Calcium: milk and other dairy products; in your bones www.wikipedia.com www.amonline.net.au Slightly less reactive than the alkali metal in the same period.
www.dentist.net 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 www.newstarget.com Bromine— dyes, pesticides, medicines Iodine— disinfectant for wounds; photography; put in table salt for health
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 www.texasphotoplus.com Neon— signs Ne— red-orange He— yellow Ar— bluish-violet Argon—most abundant Noble gas; protective gas shield for welding, light bulbs, etc. mcst.tec.me.us Krypton—used in bulbs to help them burn longer
Transition Elements 1) elements in Groups 3-12 or the “B” elements on the periodic table 2) all are metals. 3) Most found combined to form ores
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 thermometers and barometers
Inner Transition Elements Lanthanides o Also called rare earths, because at one time they were thought to be scarce o Soft enough that they can be cut with a knife o Are so similar, they are hard to separate when found together in ores
Actinides Inner Transition Elements o Are all radioactive o Most are synthetic o 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.
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 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. www.citaexam.com