Matter
Anything that takes up space and has mass
Element
A substance that cannot be broken down to other substances by chemical reactions
Compound
A substance containing two or more different elements combined in a fixed ratio
Essential elements
Elements and organism needs to survive and live a healthy life
Trace elements
Required by an organism in only minute quantities (Only some species need it)
Atom
Smallest and basic unit of matter that still retains the properties of an element
Protons
One unit of positive charge
Electrons
One unit of negative charge
Neutron
Electrically neutral
Atomic nucleus
An atom's dense central core, containing protons and neutrons
Dalton
A measure of mass for atoms and subatomic particles; the same as the atomic mass unit, or amu
Atomic number
The number of protons the element has
Mass number
The sum of the number of neutrons and protons in an atomic nucleus
Atomic mass
The precise number of protons and neutrons
Radioactive isotope
When the nucleus decays spontaneously, giving off particles and energy
Half life
The length of time required for half of the parent isotope in a sample to decay
Radiometric dating
Dates how many half lives have passed since an organism was fossilized
Energy
The capacity to cause change (ex: doing work)
Potential energy
What matter possesses because of it's own location or structure (ex: water rolling down a hill)
Electron shells
An energy level representing the distance of an electron from the nucleus of an atom. The further away from the nucleus the more energy there is
Valance electrons
The electrons in the outermost shell
Orbital
The three-dimensional space where an electron is found
Chemical bonds
The attractive forces that hold atoms together
Covalent bond
A chemical bond that involves sharing a pair of valance electrons between atoms in a molecule (formed between two non metals)
Molecule
Two or more atoms held together by covalent bonds
Single bond
A covalent bond in which two atoms share one pair of electrons (H—H)
Double bond
A chemical bond formed when atoms share two pairs of electrons in a covalent bond
Valance
The bonding capacity; the number of valance electrons required to fill the atom's outermost shell
Electronegativity
A measure of the ability of an atom in a chemical compound to attract electrons
Nonpolar covalent bond
A bond in which two atoms of the same element share electrons equally because the two atoms have the same electronegativity
Polar covalent bond
A covalent bond in which electrons are not shared equally because the atom is bonded to a more electronegative atom
Ions
Positively and negatively charged atoms
Cation
A positively charged ion
Anion
A negatively charged ion
Ionic bond
A bond formed between a cation and anion
Ionic compound
A compound that consists of positive and negative ions (NaCl)
Hydrogen bond
Weak attraction between a hydrogen atom and a electronegative atom (positive and negative bond)
Van der Walls interactions
Weak attractions between molecules that occur only when atoms and molecules are close together
Reactants
A starting material in a chemical reaction
Products
The elements or compounds produced by a chemical reaction
Chemical equilibrium
In a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time