Science Term 3

element (def)
each of more than one hundred substances that cannot be chemically changed or broken down into simpler substances and are primary constituents of matter
atom (def)
smallest unit of an element that maintains the properties of that element
atomic number (def)
the number of protons in the nucleus of an atom
atomic mass (def)
the mass of an atom
atomic mass (formula)
number of protons + number of electrons
isotopes (def)
atoms of the same element but have different numbers of neutrons
atom (structure)
radioisotope decay (def)
constant and unaffected by environmental changes
valenece electrons (def)
number of electrons in outermost energy shell
proton (def)
positively charged particle
electron (def)
negatively charged particle
neutron (def)
particle with no charge
acids and bases
the reactants in a neutralisation reaction
acid (def)
any compound that forms H+ ions in solution
base (def)
a substance that decreases the hydrogen ion concentration in a solution
carbonate (formula)
CO3 2-
strong acid (def)
an acid that ionizes completely in aqueous solution
weak acid (def)
an acid that is only slightly ionized in aqueous solution
law of conservation of mass
matter is not created nor destroyed in any chemical or physical change
chemical reaction (def)
process that changes one set of chemicals into another set of chemicals
physical reaction (def)
a change in matter that does not affect its chemical composition
reactant (def)
a substance that takes part in and undergoes change during a reaction
product (def)
a substance that forms in a chemical reaction
exothermic reaction (def)
a chemical reaction in which heat is released to the surroundings
endothermic reaction (def)
a chemical reaction that requires heat
ion (def)
an atom or group of atoms that has a positive or negative charge
ionic compound (def)
composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal
polyatomic ion (def)
an ion made of two or more atoms
transition metals (def)
groups 3-12 on the periodic table
alkali metals (def)
group 1 on the periodic table
alkaline earth metals (def)
group 2 on the periodic table
noble gases (def)
group 18 (or 8A) on the periodic table