WE ARE CHILDREN OF THE UNIVERSE STARDUST IS THE “STUFF” OF LIFE

We are the children of the Universe…… Made of the same star dust that is created and recycled in an ongoing cycle initiated with the Big Bang…..

Early Chemistry Early Chemists only believed in 1 element: Dirt Later Chemists believed in 4 elements: Air Earth Fire Water

Periodic Table of Elements Elements are Arranged according To their unique size Weight and properties

Periodic Table Notation: Chemical elements are represented on the periodic table using the following format. The letter is an abbreviation of Element Name Atomic Number is the number of protons the atom has. Mass number is the total mass of the element (protons + neutrons.

Basic Chemistry All Matter in universe is composed of Atoms Elements are composed of only 1 type of atom. ELEMENTS are pure substances that cannot be broken down or changed under ordinary means

Atoms Are the .…… Smallest piece of an element that still has all the same characteristics of that element (an atom gold, for example, is still gold) http://www.youtube.com/watch?v=cnXV7Ph3WPk&feature=related

An Atom (up close) Atoms Consist of: NUCLEUS protons neutrons Orbital Cloud electrons

Summary of Subatomic Particles:   Particle Name Location Charge Mass Electron Orbitals -1 ~0 Proton Nucleus +1 1 Neutron No Charge

Definitions to Know: Atomic Number = # of protons Atomic Mass = # of protons PLUS # of neutrons One can calculate the number of neutrons an atom has by subtracting the atomic number (# protons) from the mass number.

Isotopes: Atoms having the same atomic numbers and different mass numbers are called Isotopes Isotopes are atoms of the same element with different numbers of neutrons (mass). They react chemically the same as the “normal” form of the element They are frequently radioactive Hydrogen Isotopes

Let’s look at the isotopes of carbon There are only more neutrons in the nucleus, but the same Number of protons Atomic Mass: weighted average of the element’s isotopes

Atoms are Electrically Neutral The number of protons (+) are equal to the number of electrons (-) Therefore, atoms have no overall charge Atoms can GAIN, LOSE or SHARE ELECTRONS Electrons are involved in forming chemical bonds Atoms having a CHARGE are called IONS (we’ll discuss this later)

Interactions of Matter: Atoms interact through the process of chemical bonding. Process is determined by the number of electrons found in the outermost energy level of an atom Valence Electrons Involves the transfer & sharing of electrons between atoms. (covalent & ionic bonding)

ELECTRON / ENERGY LEVEL RULES: Atoms seek to have a “full” outermost energy level. All chemical reactions happen to accomplish this.

Why do Compounds Form? Atoms are only happy when their outermost energy level is “filled” with electrons (valence electrons) By gaining, losing or sharing valence electrons, atoms can (fill their valence shell) and find happiness The forces of attraction holding atoms together (as a result of the above) are known as CHEMICAL BONDS ATOMS SEEK STABILITY 

Involved in chemical Bonding Valence Electrons: Involved in chemical Bonding Figure 2.7

Types of Chemical Bonds Bonds holding atoms together: Ionic bonds Covalent Bonds Metallic Bonds Bonds Holding Molecules together: Hydrogen Bonds Van der Waal Forces

Ionic Bonds When an atom loses or gains electrons, it becomes electrically charged. Charged atoms are called ions. Ionic bonds are formed between oppositely charged ions. Ionic Bonds

Sodium gives away electron Chlorine IONIC BOND Positive Ion Negative Ion Opposites Attract: It’s Chemistry 

Ionic bonds are the strongest type of bond  Ionic bonds always involve: The exchange of electrons The atom that donates The electron (s) becomes A positive ion The atom that gets the Electron (s) becomes a Negative ion

Ionic Bonds: Ionic bonds form when 1 atom “gives” one or more electrons to another atom to complete their outer energy levels. This results in 1 positively charged ion & 1 negatively charged ion Since opposite charges attract, they come together and bond.

Covalent bonds involve the sharing of electrons Covalent verses ionic bond Electrons Move between Two or more Atoms This makes Both atoms Happy  Covalent bonds Not as strong as ionic

Covalent Bonds: Atoms can share more than 1 pair of electrons between them forming double and triple bonds A Molecule is a group of 2 or more atoms held together by covalent bonds.

How many pairs of electrons can atoms share ? Covalent bonds involve the sharing of electrons (no actual exchange of electrons, so no ions are formed) However, atoms can share one , two or three pairs of electrons. Single bonds result from sharing one pair of electrons Double bonds involve the sharing of two pairs of electrons Triple bonds (you guessed it) share three pairs of electrons

Covalent bonds Bonds can be ILLUSTRATED AS A straight line (s) or As electron “DOTS” The more bonds (shared electrons) between two atoms, the stronger are the forces of attraction

More on Covalent Bonding Covalent bonds can be represented as: Straight lines each line represents a shared pair of electrons. Models 2-D or 3-D molecular models

Example Formulas: Chemical Name Chemical Formula Structural Formula Water H2O Carbon Dioxide CO2 Methane CH4 Glucose C6H12O6

Structural and Chemical Formulas: Chemical formulas show the number of and types of atoms in a molecule Structural Formulas are used to graphically represent a chemical formula Useful in visualizing how chemicals react and form new ones. H20

Covalent Bonds: Covalent bonds form when 2 atoms “share” one or more electrons between them. There are 2 types of covalent bonds: Non-Polar Covalent bonds form when two atoms share electrons equally Polar Covalent bonds form when two atoms share electrons unequally.

Covalent Bonds ; NOT always is the sharing of electrons EQUAL  When electrons are not shared equally between atoms the molecule is described as being “POLAR”; This happens… When electrons are pulled closer to one atom in a molecule, a slightly negative charge develops around that atom The other atom in the molecule develops a slightly positive charge (since the electrons are pulled away)

Polar molecules are created by the unequal sharing of electrons The water molecule is a good example of a Polar covalent molecule. Notice the “slightly” Positive charge around the Hydrogen, and Negative charge around the more electronegative Oxygen

Hydrogen Bonds are forces of attraction between MOLECULES Hydrogen bonds Exist between molecules And not between The atoms of a molecule.

A HYDROGEN BOND always involves a Hydrogen atom A Hydrogen bond is an INTERMOLECULAR BOND that always involves a Hydrogen (H) atom of one molecule and an atom of another (nearby) polar molecule that has a slightly negative charge. Oxygen (O), and Nitrogen (N) are atoms often bonded to Hydrogen in a Hydrogen bond

Chemical Reactions: Reactants = Substances entering the reaction A Chemical Reactions occur whenever chemical bonds are formed or broken. Reactants = Substances entering the reaction Products = Substances existing the reaction Catalysts = Substances which speed up the rate of a reaction (enzymes are organic catalysts)

Brain Break 