Chemistry Basics

Vocabulary Atoms: Smallest particle of an element that has all the properties of matter: – Protons- particles in the nucleus with positive charge – Electrons- particles orbiting around nucleus with negative charge – Neutrons- particles in the nucleus with no charge Elements: Simplest form of a pure substance Compounds: Two or more elements chemically combined to form a new substance

Sub-Atomic Particles Part of Atom ChargeLocationMass/Size Electron - negative outside nucleus.0006 amu (too little to count) Proton + positive inside nucleus 1 amu Neutron no charge inside nucleus 1 amu

Using the Periodic Table Atomic Number Atomic Number –Equal to # protons = # electrons –Periodic Table is arranged by this number Symbol Symbol –“Shorthand” for the element – Note 2 nd letter is always lowercase Atomic Mass Number Atomic Mass Number –Total AVERAGE mass of Protons + Neutrons + Electrons 17 Cl 35.5

Electron Energy Levels Electrons are arranged in “Shells” around nucleus in predictable locations Fill “seats” closest to nucleus first (concert – best seats) “Seats” available – Shell #12 electrons – Shell #28 electrons – Shell #38 electrons – Shell #4 18 electrons – Shell #5 32 electrons – Shell #650 electrons Ex. Carbon has 6 total electrons so… Two electrons on first energy level Four electrons on second energy level Question: Could we fit more electrons on the second energy level if there were more electrons in carbon??

Ions Change in electrons which gives an atom a charge (+ or -) You can only add or subtract electrons! (protons don’t change) –Ex. Count the number of electrons below… Carbon ion (-1 charge) 7 electrons (-) 6 protons (+) Carbon ion (+1 charge) 5 electrons (-) 6 protons (+) Neutral Carbon 6 electrons (-) 6 protons (+)

Types of Chemical Bonds Ionic- Two elements bond by transferring electrons to create ions that attract together (+ is attracted to - after an electron is transferred) Covalent- Two elements bond by sharing electrons (strongest bond type) Metallic- Two metals bond and form a “common electron cloud”. This is a cluster of shared electrons (weakest bond type)

Chemical vs. Physical Change – Physical Change: A change that can occur without changing the identity of the substance. – Ex. Solid, Liquid, Gas (Phase change) – Chemical Change: Process by which a substance becomes a new and different substance – Ex. Fire

Chemical Reactions Chemical Reaction: a process in which the physical and chemical properties of the original substance change as new substances with different physical and chemical properties are formed

Chemical Reaction Basics H 2 + O 2 --> H 2 O Reactants- substance that enters into a reaction Products- substance that is produced by a chemical reaction ReactantsProducts

Evidence of Chemical Change  EPOCH is an acronym that stands for evidence that a chemical reaction has occurred. – Effervescence (bubbles and/or gives off gas) – Effervescence (bubbles and/or gives off gas) – Precipitate (solid crystals form) – Precipitate (solid crystals form) – Odor (change of smell is detected) – Odor (change of smell is detected) – Color change – Color change – Heat (reaction either heats up or cools down) – Heat (reaction either heats up or cools down)  Does sighting evidence of a chemical reaction mean that a chemical reaction has undoubtedly taken place? E P O C H

Solution Chemistry Mixtures: Matter that consists of two or more substances mixed but not chemically combined Solutions: Homogeneous Mixture in which one substance is dissolved into another » Solute = Substance that gets dissolved (ex. Kool-Aid powder) » Solvent = Substance that does the dissolving (ex. Water) Acid: Compound with a pH below 7 that tastes sour and is a proton donor. » Ex. Citrus foods Base: Compound with a pH above 7 that tastes bitter and is a proton acceptor » Ex. Cleaning Products (soap)