Chemical Compounds
Guiding Question?
How Do I determine the composition and structure of a molecule or a compound
based on its formula?
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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
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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
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Mass Number- total number of protons and
neutrons
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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
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(2) Hydrogens
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(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
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Forms when two atoms share one or more pairs of electrons
S
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Remember, there is a sharing of pairs
There is no transfer of electrons
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Can be single bonds
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Double bonds
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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
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Any positively charged atom
or group of atoms
S Anions
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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.