Atoms

Particles of an AtomAtom: smallest amount of an element

Particle Relative Mass

Charge Location Other Info

Proton 2000 + nucleus Identifies the element

Neutron 2000 No charge nucleus Proton + Neutron = mass

Electron 1 - Outside nucleus

= number of protons

Electron Cloud Model

• Electrons don’t orbit the nucleus in a pattern• Electrons dart around in energy clouds• Each cloud has its own shape

Tom Lehrer’s Element Song

Energy levels of electrons

• Energy levels are “rings” around the nucleus• Each level can hold a certain number of

electrons– Level 1: up to 2– Level 2: up to 8– Level 3: up to 18– Level 4: up to 32– The outer energy level electrons have the most

effect on the chemical properties of the element

Periodic Table of the Elements

• Atomic number• Chemical symbol• Element name• Atomic mass

Atomic number

• Is the number of protons in an atom• Is unique (identifies the element)• Equals the number of electrons in a neutral

atom• In a Periodic table, the elements are arranged

by increasing atomic numbers

Chemical symbol

• A notation of one or two letters that represent an element

• 1st letter is always capital; 2nd letter is always lower case – Examples: He, Al, Cu, Zn

Atomic mass

• Where is the mass of the atom?– Nucleus

• What particles are in the nucleus?– Protons & neutrons

• Atomic mass = number of protons + number of neutrons

• Atomic mass - # protons = # neutrons

Elements

Bellringer

Use your periodic table to determine the number of neutrons in a carbon 18 isotope