Chemical Formulas

• shorthand to describe compounds

  • uses atomic symbols

  • subscripts to describe how many atoms

  • parentheses to clarify and add extra info

• (NH4)3PO4

  • 3 nitrogen

  • 12 hydrogen

  • 1 phosphorus

  • 4 oxygen

• hydrate formulas

  • fixed number of water molecules

  • water of hydration

  • Prefixes for water molecules

• empirical formula- simplest ratio of atoms (in a crystal)

• covalent bonds use molecular formulas

• structural formula- show how atoms are connected

Chemical Reactions and Equations

• reactants → products

  • chemical equations show this process

• substances are usually in the 3 states of mater

  • solid

  • liquid

  • gas

• aq means a substance was dissolved in an aqueous solution

• state is normally not needed in a chemical equation

• Balancing a Chemical Equation

  • chemical equations have to be balanced

    • same number of atoms on each side of the equation

    • satisfies the law of conservative matter (matter cannot be created or destroyed)

  • balanced by the appropriate coefficients in front of the formulas

    • coefficient- multiplies the whole equation by that whole number

  • you have to count the number of each atom on each side of the equation

  • balance the equation one atom at a time by adding the appropriate coefficient

  • then recount every atom again

  • easier if you do the complicated molecules first

  • you can make a table of the atoms to keep track better

• Simplest Coefficients

  • Properly balanced equations have the smallest number coefficients possible

• Reaction Types

  • many chemical reactions are in distinct groups with very distinct similarities

  • when we classify the reactions we can then compare them

• Combustion Reactions

  • organic compounds react with oxygen to form carbon dioxide and water

  • if there are extra aroids then they will end up normally as elemental state products

• Single Replacement Reactions

  • elements may act with a compound to produce a new compound and a different element

• Double Replacement Reactions

  • 2 compounds react and the cation in the first equation replaces the cation in the second equation

    • basically they just switch places

• Neutralization Reactions

  • special double replacement reaction

    • one us an acid and one is a base

    • you end up with a salt and water

• Synthesis Reactions

  • 2+ elements form a compound

• Formnation Reactions

  • same a synthesis but you must have a coefficient of 1

  • you can use a fraction coefficient in these reactions

• Addition Reactions

  • a simple molecule is added to another molecule

• Decomposition Reactions

  • large molecule spilts into single elements or smaller molecules

• Net Ionic Equations

  • when ionic compounds react in aqueous solution only one ion usually reacts

  • other ions are called spectator ions

    • dont react

• Half-reaction Equations

  • used with oxidation reduction reactions

  • describing electrochemical processes

  • reduction reaction if electrons are on the reactant side

  • oxidation reaction if electrons are products

  • may be combined to make complete oxidation-reduction reactions if and only if all the electrons cancel

• Oxidation Reduction Reactions

  • involved the loss of electrons by 1 compound or ion

  • gain of the same electrons to another compound or ion

  • the two reactions can be added together

Bonding

• when atoms combine its called bonding

• valence electrons are the most important part of bonding

• if the two atoms share atoms it called a covalent bond

• if one atom loses electrons and the other one gains electrons then its ionic

• you can use electron configurations to explain how atoms bond

• nobel gases do not bond well

• Neil Bartlett made the first gas compound in 1962

• s and p sub levels are completely filled for all Nobel gases with the exception of Helium

• Ionic Substances

  • ionic bonds are the attraction of the positive charged ion to the negative charged ion

  • once we know which ions want to bond we can also predict what it will bond to

• Monatomic Ions of the Representative Elements

  • Main Group/representative elements found within the s and p blocks of the periodic table

  • elements have regular properties

  • ions of this group have some electronic configurations of the Nobel gases

  • lose electrons to form cations

  • electronic configuration allows us to know how many electrons the atom will lose

  • representative metals lose all of their valence p and s electrons

  • 4,5,6 periods contain outer s and p electrons and so they may lose the p electrons

  • representative nonmetals gain electrons to form anions

  • all halogens gain 1 electrons to for anions with 1 negative charge

• Monatomic Ions of the Non-representative Elements

  • the remaining d and f block metals

  • may have more than one possible cation

  • often form polyatomic anions

  • we can’t predict the charge of the cations

  • its not simple to figure out the appreciation of the transitional element

  • arranged by quantum number

  • allows us see more clearly which electrons are in the outermost shell of the atom

  • not all ions can be rationalized with sophistic reasoning

• Polyatomic Ions

  • many elements combine with oxygen and that forms a polyatomic ion

  • unusually stable group of atoms that ten to act as single unites during many chemical reactions

  • bound to each other with covalent bonds

• Ionic Formulas

  • formed when cations attracted to anions bc of their opposing trials

  • formulas for ionic compounds can be deduced bc no compound can have a net charge

  • total positive charge must be canceled by the negative charge

    • law of electroneutrality

  • simplest ratio is called- empirical formulkas

  • when the charge of the anion and cation are not equal you have to adjust the numbers so that they equal 0

  • when adding a subscript you need to put parentheses around the polyatomic ion before adding the subscript

• Naming Ionic Compounds

  • contain metal and nonmetal

  • names are created by giving the cation name first then anion name

  • for cation that have one possible share its just the name of the elements

  • if there is more than one charge possible then you do name then the charge in parentheses

    • i.e. lead(II)

  • anions names depend on if the anion is monatomic or polyatomic

  • monatomic named by taking first part of the element name and adding -ide

  • polyatomic ions have unique names

    • must be memorized

  • entire name is cation followed by anion name but they’re separate words

  • metals with more than 1 charge- we have to know the charge

  • ion charge is known by taking apart the formula to figure out the ion before they were bonded

• Ions in Solution

  • most ionic compounds dissolve in water

    • during this the compounds separates into cations and anions

  • symbol in parentheses designated the state of each substance

    • (s)- solid

    • (aq)- aqueous solution

    • (l)- liquid

    • (g)-gas

  • pure water can be a solid, liquid or gas

  • when substances are dissolved in water its neither pure water bonier a solution of itself

  • general principles apply to dissolution of ionic compounds

    • only 1 cation and 1 anion are formed- compounds with 3+ atoms will break apart

    • charges of ions myst add up to zero

    • subscripts of monatomic ions become coefficients for the ions

    • polyatomic ions only subscripts after parentheses become coefficients

  • any ionic compound cam be broken into cations and anions

  • solubility rules

    • compounds that have sodium or potassium alkali metals cations or the ammonium ion are soluble

    • compounds containing NO- 3 anions are soluble

• Predicting Products of Double Replacement Reactions

  • we can take 2 ionic compounds mix them together and predict the possible products

    • 2 replacements occur

• Chemical Driving Forces

  • three driving forces

    1. formation of water is the strongest

       1. ionic reaction where water is a product

    2. formation of a precipitate

    3. formation of nonionic compound from ionic reactants

  • some reactions might have 2 driving forces

• Net Ionic Equations

  • you con convert a double-replacement reaction and invert it into a net force

  • ionic reaction is obtained by writing all of the soluble ionic compounds as ions

  • then separate each compound into its ions

  • identical ions are cancelled from both sides of the equation then you get net ionic equation

  • if there is nothing less then there is no net ionic equation

• Single Replacement Reactions

  • reaction between element and ionic conmpound

  • results can be predicted like double replacement reactions

  • metal reactant form its ion and cation of the reactant becomes the element

  • reactions may be predicted when the metal reactant has only one possible cation

  • activity series- whether any given element will displace an ion in a simple replacement reaction