Adapted from Harris Middle School: NEISD Atom Notes Adapted from Harris Middle School: NEISD

An atom is the basic unit of all matter An atom is the basic unit of all matter. It is the smallest particle into which an element cannot be broken down into a simpler substance. There are 2 main locations in an atom: atomic nucleus (the center with most of the mass of the atom) electron cloud (surrounds the nucleus) There are 3 subatomic particles in an atom: subatomic means smaller (than the atom itself) 3 particles = protons, neutrons and electrons the numbers of these particles make atoms different from one another. 1 of 4

Name of subatomic particle Charge of Particle Where it is found Size/mass proton Positive (+) inside the nucleus- identifies the atom 1 atomic mass unit electron Negative (-) in electron cloud / orbiting around nucleus- determines reactivity of element Almost zero 1/1836 amu (very small!) neutron Neutral (0) inside the nucleus- just adds mass/weight 3 of 4

the atomic # = # of protons = element’s identity periodic table: chart where all elements are arranged by atomic number and properties-this is your cheat sheet to make models of atoms!! the atomic # = # of protons = element’s identity # of electrons = # of protons in an atom (neutral) Symbol is 1 or 2 letters- First letter is always capitalized; if it has 2 letters the second is lower case the atomic mass = # of protons + # of neutrons # of neutrons= atomic mass – atomic # atoms of an element can have different numbers of neutrons (these atoms are isotopes) 2 of 4

Label the subatomic particles in the picture: p+ = proton n0 = neutron e- = electron 4 of 4 Color the protons blue Color the neutrons red Color the electrons green