Chemistry vocab 2

atom
the smallest particle of a given type of matter
atomic mass unit
one-twelfth the mass of a carbon-12 atom
atomic number
the number of protons in the nucleus of an atom of an element
atomic theory
the idea that matter is made up of fundamental particles called atoms
electromagnetic spectrum
the whole range of electromagnetic radiation
electron
negatively-charged particle
electron cloud
the space around the nucleus of an atom where the atoms electrons are found
emission spectrum
the spectrum of light released from excited atoms of an element
energy level
the regions of space in which electrons can move about the nucleus of an atom
experiment
a set of controlled observations that test a hypothesis
hypothesis
a prediction that can be tested to explain observations
isotope
any of two or more atoms of an element that are chemically alike but have different masses
law of definite proportions
the principle that the elements that comprise a compound are always in a certain proportion by mass
Lewis dot diagram
a diagram where dots or other small symbols are placed around the chemical symbol of an element to illustrate the valence electrons
mass number
the sum of the neutrons and protons in the nucleus of an atom
neutron
a subatomic particle with a mass equal to a proton but with no electrical charge
nucleus
the small, dense, positively charged central core of an atom
proton
a positively charged subatomic particle
scientific law
a fact of nature that is observed so often that it is accepted as the truth
scientific method
a systematic approach used in scientific study; an organized process used by scientists to do research and to verify the work of others
theory
an explanation based on many observations and supported by the results of many experiments
valence electron
an electron in the outermost energy level of an atom