Who are you? Bond… Atom Bond! Atomic Bonding Who are you? Bond… Atom Bond!

We don’t often find atoms all by themselves… These atoms are not bonded at all. They are just flying around by themselves at many different speeds. This example would be very rare!

Instead, we usually find atoms “stuck” together… This "sticking together” is called “bonding” A combination of two or more atoms is called a molecule!

Q: So…why do atoms bond at all? A: Here this is the big “humunga bigumma” VALENCE rule: All atoms want to have a full outer shell of electrons!

Don’t forget the Valence Numbers!!! Write them down if you have not yet: +1 These numbers tell you how many e- are the valence e- !!! Full Won’t Give or take +2 The properties of Metals, Metalloids and Non-Metals tell you if they will take or give electrons to other atoms +3 +/-4 -3 -2 -1 Metalloids Can Take or Give Metals+ Get Rid of Electrons Non-Metals Take Electrons

Q: How does bonding work? One too many (+1) Room for one more (-1) We could just show you that one atom sticks to another atom, but that doesn’t show you WHY it works! - - - 11p+ (+) - - Na Cl - - - - 17p+ - - - - We need to look at our models of atoms to see the reason why atoms actually bond with each other: - - - - - Sodium Na (11): Metal Gets rid of Electrons Chlorine (17): Non Metal Takes Electrons The result is a molecule called: Sodium Chloride (Salt)

It can be easier to see bonding options with Dot models: First, let’s try the same molecule we just made: Sodium Chloride (“Salt”) - - Cl Na - - - - - - One too many (+1) NOW IT’S JUST RIGHT!!! Room for one more (-1) Now let’s try a molecule with more atoms: Dihydrogen Monoxide (“Water”) - - H - O H - - - - - One too many (+1) One too many (+1) NOW IT’S JUST RIGHT!!! Room for two more (-2) You simply fill in the empty spaces with available valence electrons!

You can even do it with many atoms into larger molecules: - H - H - H - C - C - H - C - H - H - H - C - H - H - C - H - C - C - H - H - H - H - H -

Here are some examples of these more complicated molecules: - H - H - H - H - H - H - Now try this one!!! C - H - H - H - H - H - H - H - H - H - Methane (Natural Gas) Carbon Dioxide (What humans exhale) Octane (a type of fuel) H - O - The extra electrons from Hydrogen (red) fill in the spaces on the Carbon atoms (blue) O - C - - H - H - C - H -

Ok, let’s try a few: Remember the rules you should know by now: -All atoms want to have a neutral valence (0 Charge)! -All atoms want full outer shells of e- -Opposites (+/-) attract Make a molecule for the following elements: K 4) Cl O 5) N 3) C 6) H So: Bonding happens to allow atoms to fill their outer most shells of e-

Q: What is a reaction? Reactions are when two or more atoms either bond together or split apart… Q: How do we know if a reaction has occurred? A: INDICATORS!!! (Bubbling, change of color, smell, rusting, etc…) EX: Firework Colors EX: Baking Soda + Vinegar There are many different types of reactions. We will focus on only a few:

Types of Reactions: Synthesis: A reaction that combines two or more atoms/molecules into a larger molecule A + B AB ex: Oxidation (Rust) ex: Photosynthesis (Plant food)

Types of Reactions: Decomposition: A reaction that breaks apart a molecule into smaller pieces AB A + B Explosions and Fire Splitting a substance into smaller parts Demo: Electrolysis of Dyhidrogen Monoxide

Sudden changes in Temp. Exothermic: A reaction that “feels” warm/hot Endothermic: A reaction that “feels” cool/cold Reaction Heat leaves The heat energy leaves (or exits)and warm up everything around it (like the thermometer!) Reaction Heat comes in The heat energy is absorbed and the outside is now cooler (like the thermometer!) A change in temperature without purposely adding or removing heat energy, can also indicate a chemical reaction