CHEMISTRY MIDTERM STUDY SHEET

Atomic theory

protons: positively charged

neutrons: no charge

electrons: negatively charged

atomic number: the amount of protons in an atom

atomic mass: the average atomic mass of all of the naturally occurring isotopes

mass number: the # of protons + neutrons - whole number

isotope: same number of protons but different number of neutrons

the wave-mechanical model: the electron can be found in a cloud around the nucleus

valence electrons: electrons found on the outermost shell of an atom

Contributions made by J.J. Thompson: discovered the electron using the cathode ray tube

Ernest Rutherford: discovered the proton, positive nucleus, and that most of the atom is empty space through the gold foil experiment

Half-life: the amount of time it takes for half of a radioactive element to decay or become stable.

• There are 3 types of radiation, alpha (which is a helium atom and the weakest), beta  (which is an electron and stronger than an alpha particle, and gamma  (which is pure energy, has no mass, and the strongest).

Fission: the splitting of an atom

Fusion - the joining of two nuclei into one new nucleus.

The Big Bang Theory: a theory that suggests that the universe was created as a result of an extremely large explosion.

Periodic Trends

}}atomic radius: the size of the atom}}

electronegativity: the ability for an atom to attract electrons

ionization energy: the amount of energy needed to take the most loosely bound electron

• Electronegativity and ionization energy increase as you go across a period from left to right and decrease as you go down a group.
• Atomic radius decreases as you go from left to right across a period and increases as you go down a group due to electron shielding.

Ionic compounds: form between metals and nonmetals, metals and polyatomic ions, polyatomic ions and nonmetals, and two polyatomic ions.  If the metal has more than one oxidation, then you must determine and state which oxidation is shown in the formula.  Ex; MnCl2 is Manganese (II) Chloride.  Use Table E when dealing with polyatomic ions.

ionic bonding: electrons are transferred from one element to another.

Covalent compounds: are between two or more nonmetals

covalent bonding: means that electrons are shared between nonmetals

Heating and cooling curves (phase changes)

melting: (solid to liquid)

boiling: (liquid to gas)

condensation: (gas to liquid)

freezing: (liquid to solid)

sublimation: (solid to gas skipping the liquid step)

deposition: (gas to solid skipping the liquid step)

• Kinetic energy increases when temperature increases and decreases when temperature decreases.
• During phase changes, temperature remains constant.
• Potential energy increases during melting and boiling and decreases during condensation and freezing
• When kinetic energy changes, potential energy remains constant.
• When kinetic energy stays constant, potential energy changes.
• Intermolecular forces: a force that occurs between molecules
• London dispersion forces occur between all molecules (ionic or covalent), are between nonpolar covalent molecules and is the weakest bond
• Dipole-Dipole attraction occurs between polar molecules and is stronger than London dispersion forces
• Hydrogen bonding is a special type of dipole-dipole attraction, is very strong, and occurs  between molecules hydrogen and fluorine, hydrogen and oxygen, and hydrogen and nitrogen.
• The stronger the intermolecular forces, the higher the melting and boiling point temperatures, and the greater the surface tension.
• The weaker the intermolecular forces, the lower the melting and boiling point temperatures and the weaker the surface tension.