Atom Notes Adapted from Harris Middle School NEISD

Atom Notes Adapted from Harris Middle School: NEISD

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

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 n 0 = neutron e- = electron 4 of 4 Color the protons blue Color the neutrons red Color the electrons green