Elements and Compounds

Slide 1: Elements and Compounds A Mr. Mularella Presentation

Slide 2: The 4 Ancient Elements Earth Air Fire Water

Slide 3: Elements There are currently 118 elements that  have been identified though only 88 of them are naturally occurring.

Slide 4: Elements in the Universe In our universe, hydrogen makes up 75%  of all matter! Helium makes up about 20% with oxygen  being the 3rd most abundant element. All of the other elements are relatively rare  in the universe.

Slide 5: Elements in the Earth In the Earth’s crust, oxygen is the most  abundant element (46.6%).  Silicon is the second most abundant element (27.7%).  Aluminum (8.1%), iron (5.0%), calcium (3.6%), sodium (2.8%), potassium (2.6%). and magnesium (2.1%) complete the list of elements that account for approximately 98.5% of the total mass of the earth's crust.

Slide 6: Elements Elements are a pure substance.   Made of only one kind of material, has definite properties, and is the same all throughout. Elements are the simplest pure substance.   They cannot be broken down into simpler substances without losing their identity.

Slide 7: Elements and Atoms The smallest particle of an element that  has the properties of that element is called an atom. Atoms: the building blocks of matter.  Atoms of the same element are alike;  atoms of different elements are different.

Slide 8: Chemical Symbols Shorthand way of representing the  elements. Usually one or two letters.  Usually taken from the name of the  element.  Carbon-C,Calcium-Ca, Hydrogen-H, Iodine-I, Oxygen-O, Chlorine-Cl

Slide 9: Chemical Symbols Some symbols come from their Latin  name:  Gold-Au--aurum  Silver-Ag--argentum  Iron-Fe--Ferrum  Mercury-Hg--hydrogyrum

Slide 10: Compounds Pure substances made up of more than  one element.  2 or more elements chemically combined.  Ex: H2O, NaCl, C6H12O6, CO2  Unlike elements, compounds can be broken down to simpler substances.  This can happen through a chemical reaction.

Slide 11: Compounds The properties of the elements that make  up a compound are often quite different from the properties of the compound itself.  Sodium-Na--highly reactive metal  Chlorine-Cl--poisonous gas  Sodium Chloride-NaCl--table salt

Slide 12: Molecules Compounds are made of molecules.  A molecule is 2 or more atoms chemically bonded.  Water-2 atoms of hydrogen and one atom of oxygen-  together they form one molecule of H2O. A molecule is the smallest particle of a  compound that has all the properties of that compound. Just as all atoms of a certain element are alike,  all molecules of a certain compound are alike.

Slide 13: Chemical Formulas A shorthand way of representing compounds.  If chemical symbols are the “letters,” these are  the “words.” Ex: NH3 - ammonia, C3H7OH - rubbing alcohol  Sometimes, the formula represents a molecule  of a single element. These are called diatomic molecules. This is  how that element is naturally found. O2-Oxygen H2-Hydrogen Cl2-Chlorine 

Slide 14: Chemical Formulas Subscripts are small numbers used in chemical  formulas. They are placed to the lower RIGHT of the  chemical symbols. Represent # of atoms of an element in a  compound. CO2 = 1 atom of carbon and 2 atoms of oxygen.  H2SO4 = 2 atoms of hydrogen, 1 atom of  sulfur and 4 atoms of oxygen