Chemical Compounds Guiding Question? How Do I determine the composition and structure of a molecule or a compound based on its formula? S Composition of Matter S Everything in life is made of matter S You are made of star dust! S Matter is anything that occupies space and has mass S Mass is the quantity of matter an object has A review of Elements S Elements cannot be broken down chemically into simpler matter S The simplest particle of an element is an atom S Nucleus-makes up bulk of the mass S Has protons and neutrons S Atomic #- number of protons S Mass Number- total number of protons and neutrons S Remember that protons and electrons are almost always equal Isotopes S Isotopes are atoms that have the same number protons, but a different number of neutrons. S Can you think of any isotopes we commonly use in science? S Isotopes S Atoms of an element will always have the same number of protrons, however there are different numbers of neutrons. Molecule Structures Bohr-Rutherford Model Electron Dot Diagram (Lewis) Looking at Compounds S Compounds are made up of atoms of two or more elements in fixed proportions S We use chemical formulas to show the kinds and proportions of atoms in each formula S H20 S (2) Hydrogens S (1) Oxygen S Think of your molecular structure diagrams. Can you draw this compound? Chemical Bonds S Did you figure out the diagram for H2O? S Carbon, nitrogen, and oxygen all have unfilled outer electron shells. They are looking to react! S Chemical Bonds are the attractive forces that hold atoms together. There are three types. Do you remember them? S Covalent S Ionic S Van der waals-(we wont look at this) Covalent Bonding S Forms when two atoms share one or more pairs of electrons S S Remember, there is a sharing of pairs There is no transfer of electrons S Can be single bonds S Double bonds S Triple Bonds Ionic Bond S Formed when one or more electrons are transferred from one atom to another. S Atoms are electrically neutral. They have equal protons and electrons. Difference between Ionic and Covalent Bonds S Ionic bond is between a metal and a nonmetal S Covalent is between two non metals Writing Chemical Formulas S First you must understand S Cations S Any positively charged atom or group of atoms S Anions S Any negatively charged atom or group of atoms Writing Chemical Formulas S Identify the symbol of the cation and the anion S Identify the valence or the charge of each symbol and place it just above the symbol S Balance the total positive and negative charge on the cation and anion. Charges must balance each other out S Once you determine the number of units of each the cation and anion, these become the subscripts S Lets try a few S Copper Oxide S Calcium Nitride Need an easier way? S Write the symbols of the two elements S Write the valence of each as superscripts S Drop the positive and negative signs S Crisscross the superscripts so they become subscripts S Reduce when possible S Boron oxide S Lead Oxide S Aluminum phosphide Bond with a Classmate S Take your ion and find someone you can bond with S Attempt to create the compound H2O, MgCl2..and so on S We will come together as a class and try to figure out if you are correct S If you are correct we will figure out the name of your new compound.