Physical science

• Elements


  • gold
  • silver
  • helium
  • oxygen
  • mercury
  • hydrogen
  • sodium
  • nitrogen
  • niobium
  • neodymium
  • chlorine
  • carbon
• 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
• The elements, alone or in combinations, make up our bodies, our world, our sun, and in fact, the entire universe
• The most abundant element in the earth's crust is oxygen
• 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 periodic table
  • You can predict with reasonably good accuracy the physical and chemical properties of the element
  • You can predict what other elements a particular element will react with chemically
  • Understanding the organization and plan of the periodic table will help you obtain basic information about each of the 118 known elements
• Atomic number


  • Refers to how many protons an atom of that element has
  • No two elements have the same atomic number
• Atomic mass


  • Refers to the "weight" of the atom
  • It is derived at by adding the number of protons with the number of neutrons
• This is a helium atom. Its atomic mass is 4 (protons plus neutrons)
• What is its atomic number?
• Isotopes


  Atoms that have more or less neutrons than protons
• Atomic mass unit (AMU)


  • The unit of measurement for an atom
  • One AMU is equal to the mass of one proton
  • There are 6 X 10^23 or 600,000,000,000,000,000,000,000 amus in one gram
  • Electrons are 2000 times smaller than one amu
• Symbols


  • All elements have their own unique symbol
  • It can consist of a single capital letter, or a capital letter and one or two lower case letters
• Valence electrons


  • The electrons in the outer energy level of an atom
  • These are the electrons that are transferred or shared when atoms bond together
• Metals


  • Good conductors of heat and electricity
  • Shiny
  • Ductile (can be stretched into thin wires)
  • Malleable (can be pounded into thin sheets)
  • Reactive with water resulting in corrosion
• Non-metals


  • Poor conductors of heat and electricity
  • Not ductile or malleable
  • Solid non-metals are brittle and break easily
  • Dull
  • Many are gases
• Metalloids


  • Have properties of both metals and non-metals
  • Solids that can be shiny or dull
  • Conduct heat and electricity better than non-metals but not as well as metals
  • Ductile and malleable
• Families (groups)


  • Columns of elements with similar but not identical properties
  • All elements in a family have the same number of valence electrons
• Periods


  • Horizontal rows of elements where properties change greatly across the row
  • The first element in a period is always an extremely active solid, the last element is always an inactive gas
• Hydrogen


  • Sits atop Family AI but is not a member
  • A gas at room temperature
  • Has one proton and one electron in its one and only energy level
  • Only needs 2 electrons to fill up its valence shell
• Alkali metals


  • Found in the first column of the periodic table
  • Atoms have a single electron in their outermost level
  • Shiny, have the consistency of clay, and are easily cut with a knife
  • The most reactive metals
  • React violently with water
  • Never found as free elements in nature, always bonded with another element
• Reactivity


  • Elements that are reactive bond easily with other elements to make compounds
  • Some elements are only found in nature bonded with other elements
  • Reactivity is caused by an incomplete valence electron level
  • Atoms bond until the outermost energy level has 8 electrons (rule of octet)
• Alkaline earth metals


  • Never found uncombined in nature
  • Have two valence electrons
• Transition metals


  • Include the B families
  • Good conductors of heat and electricity
  • Compounds are usually brightly colored and used to color paints
  • Have 1 or 2 valence electrons which they lose when forming bonds
  • Some can lose electrons in their next-to-outermost level
  • Combine with oxygen to form oxides
• Boron family


  • Named after the first element
  • Atoms have 3 valence electrons
  • Includes a metalloid and the most abundant metal in the earth's crust (aluminum)
• Carbon family


  • Atoms have 4 valence electrons
  • Includes a non-metal, metalloids, and metals
  • Carbon is the "basis of life" and has an entire branch of chemistry devoted to it (organic chemistry)
• Nitrogen family


  • Named after the element that makes up 78% of our atmosphere
  • Includes non-metals, metalloids, and metals
  • Atoms have 5 valence electrons and tend to share electrons when bonding
• Oxygen family


  • Atoms have 6 valence electrons
  • Most elements share electrons when forming compounds
  • Oxygen is the most abundant element in the earth's crust and extremely active
• Halogen family


  • Includes fluorine, chlorine, bromine, iodine, and astatine
  • Have 7 valence electrons, making them the most active non-metals
  • Never found free in nature
  • Only need to gain 1 electron to fill their outermost energy level
  • React with alkali metals to form salts
• Noble gases


  • Colorless, extremely un-reactive gases
  • Inert because their outermost energy level is full
  • Do not readily combine with other elements to form compounds
  • Include helium, neon, argon, krypton, xenon, and radon
• Rare earth elements


  • Composed of the lanthanide and actinide series
  • One element of the lanthanide series and most of the actinide series are called trans-uranium, meaning synthetic or man-made
• In 1869, Dmitri Ivanovitch Mendeléev created the first accepted version of the periodic table
• Mendeléev grouped elements according to their atomic mass, and found that the families had similar chemical properties
• Mendeléev left blank spaces to add new elements he predicted would occur
• Matter


  • All matter is composed of atoms and groups of atoms bonded together, called molecules
  • Substances made from one type of atom only are called pure substances
  • Substances made from more than one type of atom bonded together are called compounds
  • Compounds that are combined physically, but not chemically, are called mixtures
• Sodium and chlorine


  • When bonded, they make the compound sodium chloride (table salt)
  • Compounds have different properties than the elements that make them up
• Hydrogen and oxygen


  • When bonded, they make the compound water
  • When salt and water are combined, a mixture is created
• Mixtures can be separated by physical means, compounds can only be separated by chemical means, and elements are pure substances