Chemistry All matter is made up of atoms Atoms: smallest unit of matter Elements: pure substances that can not be broken down into smaller particles Compounds: substances that are made up of 2 or more elements in a fixed proportion Atoms make up elements, elements make up compounds

Atom Contents Atoms contain 3 subatomic particles: Name Charge Location Mass . Proton + Nucleus 1 a.m.u. Neutron 0 Nucleus 1 a.m.u. Electron – Orbital 0 a.m.u. A.M.U – atomic mass unit 2 locations in an atom: Nucleus – located in the center of the atom. Orbital (shell) – path around the nucleus that contains the electron(s) Orbital

The Periodic Table A table of all known elements in their non-reacting state The position in the table indicates key information for an element. The number in each box that increases by 1 when the table is read left to right is called the atomic number. The other number found in the box (usually at the bottom of the box) is the atomic mass.

Determining Contents of Atoms 3 rules to determine the number of Protons, Neutrons, and Electrons: Atomic number = # of protons Number of protons = # of electrons # Neutrons = Atomic Mass - # protons

Determining Contents of Atoms Atomic number = # of protons Number of protons = # of electrons 3. # Neutrons= Atomic Mass - # Protons Determine the number of protons, neutrons, and electrons for Hydrogen using the 3 rules above: H – Hydrogen Atomic Number = 1 Atomic Mass = 1 Protons = 1 Electrons = 1 Neutrons = 0

Isotopes Isotopes are naturally occurring elements with the same # of protons & electrons, but a different # of neutrons Has a different atomic mass Usually radioactive (unstable) Power plants – Uranium Medicine – MRI, diagnostic tracers, cancer treatments Radioactive (carbon) Dating – determining the age of objects Ex: 1H – mass 1 a.m.u.(Protium) Normal hydrogen 2H – mass 2 a.m.u. (Deuterium) 3H – mass 3 a.m.u. (Tritium) Isotopes of Hydrogen

Contents of Atoms Determine the atom contents of the following elements: Oxygen Titanium Helium Neon