Chemistry

Atoms The smallest particle into which an element can be divided and still be the same substance All living things are made of atoms

Subatomic Particles Protons: Positively charged Located in the nucleus Neutrons: No charge (neutral) Electrons: Negatively charged Located in the electron cloud (orbitals)

Electron Configuration The location within the electron cloud where the electrons are most likely to be found 1st shell holds maximum of 2 electrons All other shells hold a maximum of 8 electrons

Atomic Structure

Periodic Table

Elements on the Periodic Table Atomic Number = Protons = Electrons Atomic Weight = Protons +Neutrons

How to find numbers of… Number of protons = Atomic Number Number of electrons = Atomic Number Number of neutrons = Atomic Weight – Atomic Number *Round atomic weight to the nearest whole number before subtracting

Valance Electrons The number of electrons in the outer shell. Used for bonding

Octet Rule When bonding, each atom wants to have a full outer shell (8 valance electrons) ***Exception is Hydrogen, which can only hold two electrons in its outer shell

Bonding to Make Compounds

Compound A substance made of two or more atoms that bond together using their valance electrons Ex: H2O, CO2

Types of Bonds Ionic Bond Covalent Bond Hydrogen Bond

Ionic Bonds When bonds form between atoms by either gaining or losing electrons Results in the atom having either a positive or negative charge which is attracted to the other atom in the molecule

Ions When an atom has an electrical charge it is called an ion If an atom gains an electron it has a negative charge If an atom loses an electron it has a positive charge

Covalent Bonds When bonds form between atoms by sharing valence electrons

Polarity When shared electrons are attracted to one atom more strongly than another, so it has a slightly negative charge The other atom that the electrons are less strongly attracted to has a slightly positive charge

Hydrogen Bond When a hydrogen atom has a partial positive charge that attracts to the negative end of specific other molecules such as oxygen, nitrogen, and fluorine Often observed in water This is a relatively weak bond, but it allows water to have some special properties

Chemical Reaction The process of rearranging the bonds within two or more substances in order to form at least one new substance

6CO2 +6H20  C6H12O6 + 6O2 The number before the compound tells you how many there are of each compound Atomic symbols tell what elements are in the compound Subscripts tell how many of each element are in the compound ***Must have an equal number of each element on both sides of the reaction

Reactants A substance that is present at the beginning of a chemical reaction

Products A substance that is formed during a chemical reaction

Conservation of Mass Matter cannot be created or destroyed, only rearranged