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5-6 Test

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valence electron
electrons that have the highest energy level and are held most loosely. These are the electrons involved in bonding
chemical bond
force of attraction that holds two atoms together as a result of rearrangement of electrons
octet rule
8 valence electrons is stable
ion
atom or group of atoms that have an electric charge
polyatomic ion
ions that are made of more than one atom and react as a unit
ionic bond
attraction between two oppositely charged ions. Forms as a result of attraction between positive and negative ions. Usually occurs between a metal and a non-metal
ionic compound
contains ionic bonds
Properties of ionic compounds
strong bonds, high melting points, conduct electricity when dissolved in water
molecule
neutral group of atoms joined by covalent bonds
covalent bond
chemical bond formed when two atoms share electrons usually occurs between two non-metals
cation
postive ion, forms when atom loses electrons
anion
negative ion, forms when atom gains electrons
molecular compound
contains atoms that are covalently bonded
Double bond
when atoms share 2 pairs of electrons
Triple bond
when atoms share 3 paris of electrons
Properties of molecular compounds
weaker bonds, low melting and boiling points, don't conduct electricity when dissovled in water
Polar covalent bond
when electrons are shared unequally between atoms, one atom is pulling more on the electrons, causing a slight charge on the atoms
Non-polar covalent bond
when electrons are shared equally between atoms, all atoms pull equally on the electrons, so no charge on the atoms
alloy
mixture made of two or more elements that have properties of a metal. At least one must be a metal. Usually less likely to react with air and water than pure metals they are made of.
physical change
only alters the appearance or form of the substance
chemical change
a new substance is made. Bonds are broken and reformed during this reaction
Signs of a chemical reaction
new substance formed and change in energy always occur. Can see a change in color, bubbles, or a precipitate
Precipitate
solid forming from solution during a chemical reaction
Endotheric reaction
Energy is taken in by the reaction and the products have more energy than the reactants
Exothermic reaction
energy is released by the reaction and the products have less energy than the reactants
Conservation of mass law
Mass can not be created nor destroyed during a chemical reaction. This is why chemical equations must be balanced.
Open system
Matter is able to leave the reaction area and is not easily collected
Closed system
All matter is contained in a sealed container
Synthesis reaction
two or more elements combine to make a more complex substance
Decomposition reaction
breaks down compounds into simplier products
single replacement reaction
one element replaces another in a compound
double replacement reaction
elements in one compound appear to trade places with elements of the other compound
activation energy
minimum amount of energy needed to start a chemcial reaction
catalysts
material that increases the rate of a reaction by lowering the activation energy. Provides a surface for the reaction to take place
enzyme
biological catalyst contained in human cells. Only works under certain conditions
inhibitor
materal used to decrease the rate of reaction, prevents the reactants from forming the product
surface area
an increase of this causes more particles to be exposed to the reactant and increases the rate of the reaction
temperature
an increase of this causes the paricles of the reactant to speed up and collide with each other more often, which speeds up the reaction rate
concentration
an increase of this causes more reactants to be in a confined area, this causes them to collide more often and increases the reaction rate
reactants
found on the left side of a chemical equation, what you start the chemical reaction with
product
found on the right side of the equation, what you end up with after a chemical reaction
subscript
small number below an atom in a compound, tells ration of atoms in a compound
coeffiicient
a number written in front of a chemical formula (symbol for compound) to indicate the number of molecules present in a chemical equation/reaction
chemical formula
symbols used to show what elements are in a compound
chemical equation
the short and easy way to show what happens in a chemical reaction