DFA chem exam vocab

mass number

Number of neutrons and protons in nucleus

atomic number

Number of protons in nucleus

isotope

Same number of protons and electrons but different number of neutrons

average atomic mass

Weighted average of all of the isotope's mass numbers found in nature

valence electrons

Electrons in the outermost shell (can be easily shared, gained or lost)

Lewis Structures

electronegativity

A measure of the ability of an atom in a chemical compound to attract electrons

ionization energy

The amount of energy required to remove an electron from an atom

covalent bond

A chemical bond that involves sharing a pair of electrons between atoms in a molecule

dipole-dipole attraction

Attractive force resulting when polar molecules line up so that the positive and negative ends are close to each other

electrostatic repulsion

Describes a force between particles with opposite electrical charges that causes them to push apart from one another

hydrogen bond

A relatively weak bond formed between any hydrogen atom (which is covalently bound to a nitrogen or oxygen atom) and a nitrogen or oxygen with an unshared electron pair

ionic bond

Formed when one or more electrons are transferred from one atom to another

London dispersion forces

The intermolecular attractions resulting from the constant motion of electrons and the creation of instantaneous dipoles

metallic bond

A bond formed by the attraction between positively charged metal ions and the electrons around them

stable octet

The arrangement of eight electrons in the outermost shell of an atom

binary compound

What ionic compounds are called when they are composed of only two different kinds of atoms.

coefficient

A number in front of a chemical formula in an equation that indicates how many molecules or atoms of each reactant and product are involved in a reaction.

empirical formula

Simplest whole \# ratio of atoms in a compound

formula mass

The sum of the average atomic masses of all the atoms represented in the formula of any molecule, formula unit, or ion

molecular mass

The sum of the masses of all the atoms in a molecule

percent composition

The percentage by mass of each element in a compound

polyatomic ion

A covalently bonded group of atoms that has a positive or negative charge and acts as a unit

products

The elements or compounds produced by a chemical reaction.

reactants

A substance that takes part in and undergoes change during a reaction

Kinetic-Molecular Theory

A theory that explains that the behavior of physical systems depends on the combined actions of the molecules constituting the system

alloy

A mixture of two or more metals

boiling point

The temperature at which a liquid changes to a gas

colligative property

A property of a solution that depends on the number, not the identity, of the solute particles.

concentrated

Describes a solution that has a relatively large amount of dissolved solute

dilute

To lessen the concentration, force, or purity of by adding something

endothermic

A chemical reaction that absorbs energy (heat)

exothermic

A chemical reaction that releases energy (heat)

heat of fusion

Amount of energy required to change a substance from the solid phase to the liquid phase.

heat of vaporization

The amount of energy required for the liquid at its boiling point to become a gas

Le Chatelier's Principle

States that if a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress.

molarity

A common measure of solute concentration, referring to the number of moles of solute per liter of solution.

polarity

A lack of electrical symmetry in a molecule. Charge differences on opposite ends of a structure.

saturated

Unable to dissolve any more solute

solute

A substance that is dissolved in a solution.

solvent

A liquid substance capable of dissolving other substances

sublimation

A change directly from the solid to the gaseous state without becoming liquid

surface tension

An inward force that tends to minimize the surface area of a liquid; it causes the surface to behave as if it were a thin skin

activation energy

The minimum amount of energy required to start a chemical reaction

catalyst

A substance that initiates or accelerates a chemical reaction without itself being affected

collision theory

Atoms, ions, and molecules can react to form products when they collide, provided that the particles have enough kinetic energy and the correct orientation

factors affecting reaction rates

Temperature, concentration, particle size, and the use of a catalyst

enthalpy

The heat content of a system at constant pressure

entropy

A quantitative measure of disorder or randomness

equilibrium

A dynamic condition in which two opposing changes occur at equal rates in a closed system

Gibbs free-energy equation

ΔG\= ΔH(enthalpy)- TΔS(entropy)

acid

A substance that increases the hydrogen ion concentration of a solution.

base

A substance that decreases the hydrogen ion concentration in a solution.

conjugate acid

The particle formed when a base gains a hydrogen ion

Arrhenius Theory

Acids are characterized by their have H+ in the formula, sour taste, low pH, and the fact that they turn litmus red. Bases are characterized by their having OH- in the formula, bitter taste, slippery feel, high pH, and the fact that they turn litmus paper blue

conjugate base

Particle that remains when an acid has donated a hydrogen ion

endpoint

The point in a titration at which the indicator changes color

equivalence point

The point at which the two solutions used in a titration are present in chemically equivalent amounts

indicator

A compound that changes color in the presence of an acid or a base

Bronsted-Lowry Theory

Defines acids as proton donors and bases as proton acceptors; recognizes that acids and bases do not need to exist in aqueous (water) solutions; explains how acids and bases react to neutralize each other and produce water and salts when combined

neutralization

A reaction of an acid with a base, yielding a solution that is not as acidic or basic as the starting solutions were.

pH

A numeric scale used to specify the acidity or basicity of an aqueous solution

salt

An ionic compound made from the neutralization of an acid with a base.

titration

A measured amount of a solution of unknown concentration is added to a known volume of a second solution until the reaction between them is just complete

anions

Negatively charged ions

cations

Positively charged ions

combustion

A rapid reaction between oxygen and fuel that results in fire

ionization

Process in which electrolytes dissolve in water and separate into charged particles

metalloid

Demonstrate properties of both metals and nonmetals. Examples are silicon and arsenic.

transition elements

Groups 3-12

Ideal Gas Law

melting point

Temperature at which a substance changes from solid to liquid

atom

Fundamental particle of matter

proton

Positively charged atomic particle

neutron

Atomic particle with no charge

electron

Negatively charged atomic particle

electron cloud

Area surrounding the atomic nucleus

nucleus

Location of the protons and neutrons

energy level

Defined by Bohr; key to the horizontal organization of the periodic table

orbital

Defined by Schrodinger/Heisenberg; areas of probable locations of electrons within the cloud

atomic notation

element

Composed of only 1 type of atom

compound

Composed of bonded atoms of different elements

nuclear fusion

Process responsible for the formation of all elements larger than hydrogen

atomic (emission) spectrum

ground state

Lowest energy state of any electron

quantum

Discrete amount of energy required for a transition

group

Set of representative elements with the same number valence electrons

period

Set of elements with electrons in the same valence shell

Coulomb's Law

Larger and closer charges experience a greater force

shielding

Explains why the nucleus has less attraction for valence electrons in more distant energy levels

periodic trend

A property of atoms/ions that is dependent on its placement on the periodic table

atomic radius

Essentially the size of an atom

Ionic radius

Generally larger for anions and smaller for cations

electron configuration notation

ion

Charged atom

chemical property

Can only be observed when a substance undergoes a chemical change

metal

Exhibits luster, malleability, ductility, high boiling point, and low specific heat capacity

nonmetal

Exhibits brittleness, low boiling point, high specific heat capacity

s orbital

Fits 2 electrons