Chemistry Notes for Chapters 2-4
Atoms


-Elements
-Compounds
Compounds
-Molecular (non metals and neutral)
 CO2, SO2
-Ionic
 Cl-, Na2
Atomic Theory
1. Elements are composed of extremely small particles
2. All atoms of a giver element are identical, having the same size, mass, and
chemical properties
3. Compounds are composed of atoms of more than one element
4. A chemical reaction involves only the separation, combination, or rearrangement
of atoms, it does not result in their creation or destruction
Nomenclature

Ions-either cations which are positively charged or anions which are negatively
charged
-examples of anions: e- +F- = flouride
Chlorine atom + e- = Chloride Cl-examples of cations: Na+ + 1e- = Na Sodium atom

Ionic compounds [cations][anion]
-Na+ + Cl- = Sodium Chloride
-K+ + S2- = K2S or Potassium sulfide
Structure of the Atom
Atoms-basic unit of an element
Electron-Negatively charged particles
Nucleus-where the positive charges are concentrated (protons)
Neutron-proved to be electrically neutral particles having a mass of slightly greater than
that of protons
Atomic Number
The number of protons in the nucleus of each atom of an element is its atomic number. In
a neutral atom the number of protons is equal to the number of electrons so that atomic
number also indicates the number of electrons present in the atom
Mass Number
Is the total number of neutrons and protons present in the nucleus of an atom of an
element.
Mass Number = number of protons + number of neutrons = atomic number + number of
neutrons
Periodic Table
Periodic Table-a chart in which elements have similar chemical and physical properties
are grouped together.
Periods-Horizontal rows
Groups-Vertical Rows
Metals-good conductor of heat and electricity
Non Metals-a poor conductor
Metalloid-properties that are intermediate between metals and non-metals
Group IA-alkali metals
Group IIA-alkali earth metals
Group VII A-halogens
Group VIIIA-noble gases
Molecules
Molecules-an aggregate of at least two atoms in definite arrangement held together by
chemical bonds.
Diatomic molecule-contains 2 atoms
Poly-atomic-contains more than 2 atoms
Chemical Formulas
Molecular formula-shows the exact number of atoms of each element in the smallest unit
of an element
Empirical formula- tells us which elements are present and the simplest whole number
rations of their atoms
Naming Compounds
Organic Compounds-contain carbon, usually in combination with elements such as
hydrogen, oxygen, nitrogen, and sulfur
Ox ions
ClO3- chlorate
ClO4- perchlorate
BrO4- perbromate
Bro3- bromate
NH4- ammonium
Acids and Bases
Acids-a substance that yields hydrogen ions when dissolved in water
Formulas for acids contain one or more hydrogen atoms as well as an anion group
Bases-a substance that yields hydroxide ions when dissolved in water
Chapter 3
Mass Relationships in Chemical Reactions
Molar Mass-defined as mass of 1 mole of units
If we know the atomic mass of an element we also know its molar mass
Molecular mass-sum of the atomic masses in a molecule
Percent Composition-percent by mass of each element in a compound
Reactions-steps to figure out a reaction
1.
2.
3.
4.
balance
input information given
identify the goal
crate a path to reach the goal
Chemical Reactions- process in which substance is changed into one or more new
substance
Equations- uses chemical symbols to show what happens during the reaction
Chapter 4
Reactions in Aqueous Solutions
Solutions-a homogenous mixture of 2 or more substances
Solute-substance present in smaller amounts
Solvent-the substance present in larger amounts
What happens when solute dissolves in water
1. Electrolytes
- strong: ionic compounds
- weak: acids and bases
2. Non Electrolytes
- molecular compounds
Electrolytes-solution that can conduct electricity, forms both positive and negatives
Non electrolytes: Solution does not conduct electricity
Types of Reactions
1. Precipitation Reactions
2. Acid Base Reactions
Precipitate Reactions
Precipitate-insoluble solid that separates from solution
Acid Base Reactions
Acid-have a sour taste, vinegar owes its taste to acetic acid
Bases-have bitter taste, feel slippery, cause color changes in plant dyes
Examples
Weak Base:
Ammonium Hydroxide
Strong Acid:
Nitric Acid
Sulfuric Acid
Weak Acid:
Nitrous Acid
Acetic Acid
When you have Oxidation Reduction reactions
Reduction gains electrons
Oxidation loses electrons
Oxidation number-the charge that atom would have in a molecule if electrons were
completely transferred.
1. Free elements have an oxidation number of 0
2. In monoatomic ions the oxidation number is equal to the charge of the ion
3. Always-Group 1A metals are +1 and Group 2A metals are +2
4. Most cases H is +1 except when it is bonded to metals, and O is 2- except when it
forms peroxide.
5. The sum of the oxidation number of all atoms in a molecule or ion is equal to the
charge of the molecule or ion
Redox Reactions
1.
2.
3.
4.
5.
Combination
Decompostion
Combustion
Disproportionation
Displacement