Science – Atomic Structure Study Guide

basic unit of matter; consists of three main types of subatomic particles: protons, neutrons, and electrons.
Pure substance consisting of one type of atom(s).
Dense region at center of atom
Subatomic particle with positive electrical charge in nucleus of atom
Subatomic particle with no electrical charge, mass slightly larger than proton; located in nucleus
negatively charged particles that have relatively no atomic mass; orbits nucleus in electron cloud (electron shell or ring)
electron shell
orbit followed by electrons around an atoms nucleus
valence electrons
electrons on the outermost energy level of an atom
chemical symbol
a one or two letter representation of an element; 3 letter if its a temporary symbol
atomic number
the order of an element in periodic table of the elements; or corresponds to number of protons
atomic mass
total mass of the protons and neutrons in an atom, measured in atomic mass units
horizontal rows in the periodic table
vertical columns of the periodic table
noble gases
one of the elements of group 18 of the periodic table (helium, neon, argon, krypton, xenon, and radon); noble gases are unreactive; have low chemical reactivity
chemical reactivity
tendency for elements to participate in a chemical reaction
low chemical reactivity
outer rings are full giving them little tendency to participate in chemical reactions
high chemical reactivity
outer rings are not full; giving them higher tendency to participate in chemical reactions
One of a class of elements that are good conductors of heat and electric current; metals tend to be ductile, malleable, and shiny; typically solid at room temperature
elements that are usually dull in appearance, poor conductors of heat and electricity, gases at room temperature; melt at low temperatures
are the elements on or near the zip-zag line; have the properties of both metals and nonmetals
elements in period table are arranged according to increasing number of these
each element in the same row has the same number of energy levels
energy levels
also called electron rings or electron shells
these columns, also called families of elements, have the same number of valence electrons
an atom that has the same number of protons (or the same atomic number) as other atoms of the same element do but that has a different number of neutrons (and thus a different atomic mass)
a particle that is electrically charged (positive or negative)
electrically neutral
atom that has equal number of protons & electrons; net charge equal to zero