 Chemical Compounds Guiding Question? How Do I determine the composition and structure of a molecule or a compound based on its formula?

Composition of Matter  Everything in life is made of matter  You are made of star dust!  Matter is anything that occupies space and has mass  Mass is the quantity of matter an object has

A review of Elements  Elements cannot be broken down chemically into simpler matter  The simplest particle of an element is an atom  Nucleus-makes up bulk of the mass  Has protons and neutrons  Atomic #- number of protons  Mass Number- total number of protons and neutrons  Remember that protons and electrons are almost always equal

Isotopes  Isotopes are atoms that have the same number protons, but a different number of neutrons.  Can you think of any isotopes we commonly use in science?  Isotopes Isotopes  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  Compounds are made up of atoms of two or more elements in fixed proportions  We use chemical formulas to show the kinds and proportions of atoms in each formula  H20  (2) Hydrogens  (1) Oxygen  Think of your molecular structure diagrams. Can you draw this compound?

Chemical Bonds  Did you figure out the diagram for H2O?  Carbon, nitrogen, and oxygen all have unfilled outer electron shells. They are looking to react!  Chemical Bonds are the attractive forces that hold atoms together. There are three types. Do you remember them?  Covalent  Ionic  Van der waals-(we wont look at this)

Covalent Bonding  Forms when two atoms share one or more pairs of electrons  Remember, there is a sharing of pairs  There is no transfer of electrons  Can be single bonds  Double bonds  Triple Bonds

Ionic Bond  Formed when one or more electrons are transferred from one atom to another.  Atoms are electrically neutral. They have equal protons and electrons.

Difference between Ionic and Covalent Bonds  Ionic bond is between a metal and a nonmetal  Covalent is between two non metals

Writing Chemical Formulas  First you must understand  Cations  Any positively charged atom or group of atoms  Anions  Any negatively charged atom or group of atoms

Writing Chemical Formulas  Identify the symbol of the cation and the anion  Identify the valence or the charge of each symbol and place it just above the symbol  Balance the total positive and negative charge on the cation and anion. Charges must balance each other out  Once you determine the number of units of each the cation and anion, these become the subscripts  Lets try a few  Copper Oxide  Calcium Nitride

Need an easier way?  Write the symbols of the two elements  Write the valence of each as superscripts  Drop the positive and negative signs  Crisscross the superscripts so they become subscripts  Reduce when possible  Boron oxide  Lead Oxide  Aluminum phosphide

Bond with a Classmate  Take your ion and find someone you can bond with  Attempt to create the compound H2O, MgCl2..and so on  We will come together as a class and try to figure out if you are correct  If you are correct we will figure out the name of your new compound.