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Basic Chemistry
Atoms, Elements & Molecules
Atoms Around Us
“To understand the very large, we must understand the very small”
Democritus Atoms
Atomos (indivisible)
Atom Anatomy
Electrons Negative charge
Protons Positive charge
Neutrons Neutral
Atomic Number
Each atom has electron orbitals (energy levels) If completely filled, the atom is stable If not completely filled, the atom is unstable
2n2
Elements are arranged according to their atomic number.
Electron Dot Diagrams
Periodic Table
Dimitri Ivanovich Mendelèev (1834 – 1907) Organized elements in order of increasing atomic
weight
Atomic weight is the average mass of the atoms in a representative sample of an element.
Isotopes Atoms with the same number of protons, but different
number of neutrons
Periodic Table
Groups (families) Periods
Periodic Table
Metals Nonmetals Group IA = Alkali metals Group IIA = Alkaline earth metals Group VIIA = Halogens
Extreme right = Noble gases Group B = Transition metals
Metals
Four characteristics:
1. Conduction
2. Reactivity
3. Chemical
4. Alloys
Happy Noble Gases
These elements are in Group VIIIA 8 electrons in the outer orbital
The fact that their outer orbitals are full means they are quite happy not reacting with other elements
Helium Neon Argon Xenon
Transition Metals
Advanced orbital rules In general, they are
elements in which the inner electron energy levels are being filled.
In other words, they are able to use the two outermost orbitals to bond with other elements.
Ions
Ions are atoms with either extra electrons, or missing electrons In other words, the number of electrons are not
equal to the number of protons.
Cations sodium
Anions chloride
Ionic Bonds
Generally speaking, those elements on the left hand side of the table react with those elements on the far right (excluding the noble gases) to form stable crystalline solids.
Metals give up electrons to elements on the right (nonmetals).
Covalent Bonds
Shared pairs of electrons
Many elements are diatomic Meaning that they can attach to each other For example, chlorine atoms:
Cl
Chemical Reactions
Chemical change must occur. A reaction could include ions, molecules, or
pure atoms. Reaction Rate & Collision Theory
Concentration Temperature Pressure
Chemical Equations
Law of Conservation of Mass
Reactants Products Catalysts Inhibitors
Balancing Chemical Equations
A silver spoon tarnishes. The silver reacts with sulfur in the air to make silver sulfide, the black material we call tarnish:
___ Ag + ___S → ___Ag2S
Types of Chemical Reactions
Composition (Synthesis) A + B → AB
Decomposition (Desynthesis) XY → X + Y
Single Replacement AB + C → CB + A
Double Replacement AB + CD → AD + BC
Endothermic Requires heat energy
Exothermic Releases heat energy
Formation of a Precipitate
Chemical Reaction Properties
Reversible Equilibrium
Acids & BasesSvante Arrhenius (1887)
ACIDS1. Turn indicator dye litmus
from blue to red
2. React with active metals such as zinc, iron, and tin, dissolving the metal and producing hydrogen gas
3. Taste sour, if diluted enough to be tasted safely
4. React with certain compounds called alkalis or bases to form water and compounds called salts
BASES1. Turn the indicator dye
litmus from red to blue
2. Feel slippery or soapy on the skin
3. Taste bitter
4. React with acids to form water and salts
Acids
Arrhenius proposed that these characteristic properties of acids are actually properties of the hydrogen ion (H+), and that acids are compounds that yield H+ in aqueous solutions. Slightly modified today
Hydronium ion (H3O+) For simplification, we’ll stick with the H+
terminology.
Acids
Monoprotic One H+
Diprotic Two H+
Triprotic Three H+
Polyprotic General term for acids
that give up more than one H+
Strong Acids Ionize completely (or
nearly completely) in water
HCl (hydrochloric acid)
Weak Acids Ionize only slightly in
water CH3COOH (acetic acid)
Bases
Yield hydroxide ions (OH-) in aqueous solutions
Monobasic One hydroxyl anion
Dibasic Two hydroxyl anions
Tribasic Three hydroxyl anions
Polybasic General term for bases
that give up more than one OH-
Strong Bases Completely ionize
NaOH (sodium hydroxide; lye)
All the bases of Group I and Group II are strong bases
Weak Bases NH3 (ammonia)
pH Scale
pH = -log [H+]
Brønsted-Lowry Acid-Base Theory
By the 1920’s chemists were working with solvents other than water.
Acid Proton (H+) donor
Base Proton (H+) acceptor
Acid-Base Titrations Method used to
determine just how much acid (or base) there is in a solution of unknown concentration
Buret A piece of laboratory
glassware designed to deliver known amounts of liquid into another container
A Word About Moles…. A mole used in chemistry is something like
the dozen we use every day.
A mole simply means that you have 6.02 x 1023 of whatever you’re talking about. Avogardo’s number
Molarity is defined as the number of moles of solute divided by the number of liters of solution Molarity (M) = moles of solute
liters of solution
Lab Prep (Tomorrow)
Salinity & Conductivity SPM filter prep. Glassware Use
Pipettes Dilutions of copper II sulfate
Burets Acids & Base Titration
Nutrients Prep. of standards for nutrient analysis
Lab Prep (Next Week - Sierra)
Field Trip to collect water for nutrient analyses Salinity, DO, and pH will be recorded on site Nutrients measured the week after in the lab
Watershed Readings North Carolina Division of Water Quality