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Science Chap.7&8

Terms

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Polyatomic Ions
~A group of covalently bonded atoms that act as a single atom when bonding with other atoms.
~ Bonding woth polyatomic ions are covelant but they bond using ionic bonds with other atoms
Synthesis
Two or more smaller substances combine to form one bigger, more complex substance
Rates of Chemical Reactions
~Kinetics is the study of reaction rates
~Collision Theory how fast a reaction occurs depends on four things
~Concentration
~Surface Area
~Temperature
~Catalyst
Surface Area
~The greater the sirface area the faster the reaction rate
~To increase the rate of the reactoin you can break reactants into smaller pieces
Activation Energy
Energy required for a chemical reaction to occur
Endothermic Reaction
Energy is absorbed
Metallic Bonds
~Occurs between two non-metals
~They a common electron cloud or sea of electrons
~The positive nucleus is attracted the surrounding electrons
Oxidation Number
~The number of electron lost, gained, or shared during a chemical bond
~It is used to predict how the atoms will combine and what formula the resulting compound will be
~#1 rule the sum of the oxidation numbers must be zero
Catalyst
~A substance that increases the rate of a reaction but is not itself changed by the reaction
~ It causes the activation energy needed to decrease
Chemical Bonding
~The combining of elements to form new substances.
~The electrons involved in chemical bonding are valence electrons.
~Three types of bonding Ionic, Covalent, and Metallic
Chmeical Reactions
~Process in which the phys. and chemical properties of the original substances change as new substances with different phys. and chemical properites form
~Reactants yield products
~Energy is either abosrbed or realeased during a chemical reaction
Temperature
~As temperature increases the reaction rate increases
~As temperature increases the amount of collisions increase as does the force with which the they collide making a greater percentage of the collisions "Effective Collision"
Ionic Bonding
~Bonding that involves the transfer of electrons
~Form ions which are charged atoms
~Ionic bonds tend to from between metals and non-metals
Types of chemical reactions
~There are four types
~Synthesis
~Decomposition
~Single Replacement
~Double Replacement
Crystals
~The placement of ions in an ionic compound results in a regular, repeating. pattern called a crystal lattice.
~Crystals have high melting points and are very stable
Electron Affinity
~The tendency of an atom to gain electrons
~As you go across the periodic table the electron affinity increases
~Flourite has the highest electron affinity
Concentration
~The higher the concentration the greater the reaction rate
~ In a reversible reaction if the reactants concentration is increased then the reaction increases in the forward direction. If the products concentration increases then the reverse reaction's rate increases.
Decomposition
Breaking a complex compound into two or more substances
Molecules
~Combination of atoms formed by a covalent bond
~Molecules usually have high melting points expcept for sand and graphite they are network solids
Double Replacement
The compounds switch partners
Exothermic Reaction
Energy is released
Covealent Bond
~The sharing of electrons between two non-metals.
ex. H2O
Single Replacement
An element replaces one of the elements in a compound

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