11 terms

Atoms and elements

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atoms
Building blocks of matter
indirect evidence
Evidence that does not involve direct observation
nucleus
A region that is located at the center of an atom and contains most of the atom's mass
electron
A subatomic particle that has a negative charge
proton
A subatomic particle that has a positive charge and that is found in the nucleus of an atom
element
A pure substance made of only one kind of atom
atomic number
Number of protons in an atom.
mass number
the sum of the number of neutrons and protons in an atomic nucleus
isotope
Atoms of the same element that have different numbers of neutrons
allotrope
Different molecular forms of the same element.
model
A simplified description designed to show the structure or workings of an object, system or concept.