Basics of Chemistry (Lecture 2)

Solid

Holds shape and fixed volume

Liquid

Shape of container, free surface, and fixed volume

Gas

Shape of container and volume of container

Element

a substance that cannot be broken down to other substances by chemical means

Compound

a substance consisting of two or more different elements (ex. H2O)

Atom

smallest unit of matter that retains the properties of an element

Protons

found in the atomic nucleus, one unit of positive charge, mass of ~1 Dalton

Neutron

found in the atomic nucleus, no charge, mass of ~1 Dalton

Electron

found outside the nucleus, one unit of negative charge, mass of 1/2000 Dalton (essentially nothing)

Atomic #

Located at the top of the element on the periodic table, and equals the amount of protons

Mass #

sum of the neutrons plus the protons in an atom

Atomic mass

mass number is an approximation of the total mass of the atom

Isotopes

the same number of protons in an element, but the number of neutrons is different.

Radioactive Isotope

an isotope in which the nucleus decays spontaneously giving off particles and energy

Molecule

two of the same or different atoms

Energy level

different states of potential energy that the electron can have represented symbolically in electron shells

Valence shell

outer shell of the atom

Valence electrons

number of electrons in the outer shell

Valence

number of missing electrons in the outer shell

Covalent bond

sharing a pair of valence electrons by 2 twos

Covalent Nonpolar Bond

bond where electrons are shared equally between atoms

Covalent Polar Bond

bond where electrons are shared unequally between atoms

Electronegative

the tendency to attract electrons and pull toward oneself to form a chemical bond

Cation

atom with a positive charge

Anion

atom with a negative charge

Ion

atom with a charge

Hydrogen bond

a weak attraction between any molecules that have partial charges

Kinetic Energy

the energy of motion

Heat

measure of the total amount of kinetic energy due to a molecule's motion in a body of matter (ice ocean)

Temperature

average kinetic energy of the molecules (hot coffee)

Solvent

dissolving agent of a solution

Solute

the substance that is dissolved

Aqueous solution

solution where water is the solvent

Hydrophilic

like water and is attracted

Hydrophobic

dislikes water and repels -- is nonionic and nonpolar

Acid

A substance that increases the hydrogen ion concentration of a solution (pH < 7)

Basic

a substance that decreases the hydrogen ion concentration of a solution (pH > 7)

Buffer

substance that minimizes changes in the concentration of hydrogen (H+) and hydroxide (OH-)