element symbol
letter code for an element that is usually one to two letters long
law of constant composition
a given compound always contains elements in exactly the same proportion by mass
Daltons Atomic Theory
theory established by John Dalton in the early 1800's, used to explain the nature of materials
Atom
fundamental units of which elements are composed
compound
substance made of 2 or more different elements joined together in a specific way
chemical formula
representation of a molecule in which the symbols for the elements are used to indicate the types of atoms present and subscripts are used to show the relative numbers of atoms
electron
negatively charged subatomic particles
nucleus
the relatively small and dense center of positive charge in an atom
proton
positively charged subatomic particle located in the atomic nucleus
neutrons
a subatomic particle in the atomic nucleus with no charge
isotope
atoms with the same number of protons but different numbers of neutrons
atomic number
the number of protons in the nucleus of a given space
mass number
total number of protons and neutrons in the nucleus of a given atom
periodic table
chart showing all the elements arranged in columns in such a way that all the elements in a given column exhibit similar chemical properties
group
vertical columns of elements on the periodic table
alkali metal
group 1A metals
alkali earth metals
group 2A metals
halogen
group 7A elements
nobel gas
group 8A elements
transition metal
several aeries of elements in which inner orbitals are being filled
metal
an element that gives up electrons relatively easily and is typically lustrous, malleable and a good conductor of energy and heat
nonmetal
element that doesnt exhibit metallic characteristics; chemically a typical nonmetal accepts electrons from a metal
metalloid
element that has both metallic, and nonmetallic properties
law of conservation of mass
mass is neither created nor destroyed
ion
an atom/ group of atoms that has a positive or negative charge
cation
positively charged ion
anion
a negatively charged ion
ionic compound
a compound that results when a meta reacts with a nonmetal to form cations and anions