Earth and Space Science Unit 2 (right one)

bohr model

a planetary-like model of the atom, proposed by Niels Bohr, where electrons orbit a nucleus in specific, quantized energy levels or paths

lewis dot diagram

another way to show an element's valence electrons; includes the symbol for the element surrounded by dots connected in rings, or the energy levels

physical change

alters the form or appearance of matter but does not turn any substance in the matter into a different substance; matter changes form but not chemical identity

chemical change

change in matter that produces one or more new substances; occurs during a chemical reaction

mixture

made up of two or more substances that are together in the same place, but their atoms are not chemically bonded and not in a set ratio, each kind of matter retains its own identity and properties

compound

a substance that is made from the atoms of two or more elements that are chemically bonded in a set ratio

element

a pure substance made of only one kind of atom; can be identified by its specific chemical and physical properties

periodic table

a chart showing all of the elements arranged according to the repeating pattern of their properties

atomic number

the number of protons in the nucleus of an atom

average atomic mass

the weighted average mass of all the isotopes of an element

mass number

the sum of the protons and neutrons in the nucleus of an atom, how an isotope is identified

isotope

atoms of the same elements that have different numbers of neutrons

amu

atomic mass unit; used to indicate mass on an atomic scale

atom

the smallest particle that can still be considered an element; the basic unit from which all matter is made; different substances are maxed up of different types of atoms

subatomic particles

protons, neutrons, electrons; particles smaller than an atom

nucleus

the center of the atom, where the protons and neutrons are located; a dense, positively charged center of an atom

electron cloud

a region around the nucleus of an atom where electrons are likely to be found

proton

a positively charged particle in an atom's nucleus

neutron

a particle in the nucleus of an atom that has no electric charge

electron

the negatively charged particles inside an atom

valence electron

the electrons that have the highest energy located in the outermost energy level; used in ionic and covalent bonding

energy level

a fixed distance from the nucleus of an atom where electrons may be found; the first energy level can hold a maximum of two valence electrons and the second can hold a maximum of eight. the outermost energy level has the highest amounts of energy

neutral

a neutral atom has a net charge of zero because the number of protons is equal to the number of electrons, the opposite charges cancel out

ion

an atom or group of atoms that either have a positive or negative charge

stable/unstable

both stable and unstable isotopes of an element have the same number of protons, just a different number of neutrons. a stable isotope is a non radioactive atom, an unstable isotope is a radioactive form of the element that will spontaneously decay

diatomic element

formed of two atoms; gases that are only found as a pair of bonded atoms

chemical reaction

a process where starting materials, called reactants, transform into different substances, called products; occur when bonds are broken and/or formed

reactant

(starting materials) written on the left side of the equation; substances that undergo chemical change

product

(ending materials) written on the right side of the equation; what chemical changes form

chemical equation

representation of chemical reactions using chemical formulas to easily and efficiently communicate what is happening at the atomic level

coefficient

a whole number placed in front of a chemical formula to tell the reader how many copies of that molecule are needed to balance the equation, involved in the reaction

subscript

a small-sized number on the bottom right of the symbol, indicates how many atoms of an element are in a compound or molecule

ionic bonding

forms when atoms are held together by the attraction between opposite charges; atoms transfer one or more electrons to become ions that attract each other; a metals transfers valence electrons to a nonmetal

covalent bonding

the chemical bond formed when two atoms share electrons in order to satisfy the octet rule

molecule

two or more atoms held together by covalent bonds one type of extended structure

monatomic ion

when a single atom forms an ion

polyatomic ion

when a group of covalently bonded atoms form an ion; an ion made of more than one atom

cation

ion with a positive charge

anion

negatively charged ion

electromagnetic force

the attraction between the positive charge on protons and negative charges on electrons. this force bonds electrons to the nucleus. because electrons are moving with momentum, they move around the nucleus instead of falling in due to the force of opposing charges

strong nuclear force

stronger than electromagnetic force, it is the strongest force known to science. this force attracts protons and neutrons together. if there are enough neutrons, the attraction from the strong nuclear force wins out over repulsion from the electromagnetic force and the nucleus stays together. this force only works at extremely small distances

weak force

is another nuclear force weaker than both the electromagnetic force and the strong nuclear force. if you leave a single neutron outside the nucleus, the weak force eventually causes it to break down into a proton and electron. the weak force only comes into play in special cases when atoms break apart

fusion

separate atoms are fused together to form a new atom; releases energy if the final nucleus has lower energy than the initial nuclei, energy is produced when atoms with a lower atomic number than iron fuse together

fission

an atom is split up into smaller atoms that have lower atomic numbers; energy is produced when the atom that is split has an atomic number higher than iron, a neutron hits a nucleus with enough energy to break it up. extra neutrons are released during the split, causing a chain reaction of fissions of other nuclei

what are the seven diatomic elements?

H2,O2,N2,Cl2,F2,Br2,I2