Campbell Unit 2

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