Organizing the Elements The Periodic Table
Elements • There are 118 different kinds of atoms. • Most matter is made up of two or more kinds of atoms, but some consist of just one type of atom. • When matter is composed of one type of atom it is called an element. • 94 elements are naturally occurring and the remaining are synthetic or unstable elements (24)
Elements Single atom of oxygen Molecule of oxygen
Element… • Element: An element is a pure substance that cannot be broken down into a simpler chemical substance by any physical or chemical means • Ex. Gold, copper, carbon, lead
Representing Elements… • Element Symbol: An abbreviation for a chemical element. • The symbols for elements are the same all over the world, regardless of the language. • The symbol of an element is taken from its name. Often the first letter is used. (Fluorine = F)
Element symbols..
The name of an element may begin with the letter of a symbol already in use. So they are named by: • The element’s first two letters, Os, for Osmium • The first letter and some other letter in the name, Cl, for Chlorine • Symbols are taken from their Greek or Latin names , Aurium for gold • Symbols are sometimes named after famous scientists or places eg. Einsteinium or Americium
Rules for writing symbols: • The symbol always begins with a capital letter • If there is a second or third letter, it is always a lowercase letter • There is no period at the end of the symbol
Early Classification of Elements… • Alphabetical, colour, taste didn’t work • Metals vs. non-metals • These just didn’t seem to cut it….
Mendeleev • Russian chemist • Organized 64 elements known at that time • He did it by atomic mass • Found similarities in physical properties of those in the same columns
Today’s Table • Periodic table: a table in which the elements are organized into rows and columns according to their atomic numbers and properties
Today’s Table • Primarily organized by; • atomic number, • metal/non-metal • properties like reactivity • Organized into groups/families and periods
The periodic Table of Elements… http://www.chemicool.com/ http://www.youtube.com/watch?v=GFIvXVMbII0
Metals, metalloids, Non-metals
Metals • Metals: an element that is lustrous, malleable, ductile and conducts heat and electricity • Even if the metal appears to be dull in colour on the surface, freshly cut a metallic sheen can be seen • Located on the left side of the periodic table
Non-metals • Non-metals: an element usually a gas or dull powdery solid that does not conduct heat or electricity. • Upper right portion of the periodic table • Bromine is the only liquid non-metal at room temperature
Metalloids • Metalloids: an element that has properties of both a metal and a non-metal. Found along the staircase line between metals and non-metals
Periods (there are 7) • Each row represents a separate period • Have the same number of electron shells (energy levels)
Groups (there are 18) • Arranged together in rows (numbered 1 to 18) • Also called a family • All elements in each group have similar properties
Group 1: Alkali Metals • React rapidly when exposed to air and water • Shiny, silvery and soft • Highly reactive, often explosive in water http://www.youtube.com/watch?v=uixxJtJPVXk
Group 2: Alkaline Earth Metals • Be, Mg, Ca, Sr, Ba, Ra • Shiny and silvery, but not soft • Less reactive than alkali metals • These metals have a distinguishable flame color, Mg & Be white, brick-red for Ca, magenta-red for Sr, green for Ba and crimson red for Ra. http://www.youtube.com/watch?v=B2ZPrg9IVEo
Group 3-12:Transition Metal • Includes Ga, In, Sn, Tl, Pb, Bi, Lu, Lr and all the Uu… metals • Low reactivity • Rare earth metals/ inner transition metals often included
Group 18: Noble Gases • Unreactive, colourless, odourless • All gases (He, Ne, Ar, Kr, Xe, Rn) • He- low density for balloons, • Used for neon signs(glow with electric current) • Ar: blue, Kr: pink/white, Xe: purple, Ne:red http://www.youtube.com/watch?v=AmTZPx1whUQ
Group 17: Halogens • Most reactive non-metals • Rarely found in elemental form • Poisonous in large amounts • Many common uses: • Chlorine: pools • Iodine: clean wounds • Bromine: halogen light bulbs • http://www.youtube.com/watch?v=u2ogMUDBaf4
Hydrogen? • As you may have noticed hydrogen is not classified with any other group • Hydrogen is unique in the sense that it has a single electron in the first orbital • Hydrogen can donate an electron like the alkali metals but can accept an electron like a halogen • Non-metal
Periodic Trends • We saw changing reactivity between groups • Group 1 more reactive than group 2 • Group 17 more reactive than group 16 in the same row • Other trends:
Other trends • As you go down a family, the number of electron orbits increases • Within a family all elements have the same # of electrons in the outer most shell • Reactivity is based on the number of electrons in the outer shell
Most reactive groups
