Matter
Matter
 Any object made by particles (atoms) that takes up
space and has mass
 Has chemical properties (reaction to other substances)
& physical properties (density, hardness, color, etc.)
Element
 Substance that can´t be broken down into any simpler
substance
 115 known elements (over 90 found in nature)
 8 make up 98% of the Earth´s crust
 Shown as a 1 or 2 letter symbol
o H = Hydrogen, C = Carbon, O = Oxygen
o He = Helium, Co=Cobalt, Ni = Nickel
o Au = Gold, Cu = Copper, Hg = Mercury
The Atom
 Basic unit of all matter
 Made of 3 particles in 2
areas
Subatomic Particles
 Proton
o Positive electrical
charge and a mass of
1 amu
 Electron
o Negative electrical
charge and no mass
 Neutron
o No electrical charge (neutral) and mass of 1 amu
Inside the Atom
Atom is held together in part due to electrical attraction
Like charges (+ and + or – and –) repel while unlike
charges (+ and –) attract
Atoms have equal numbers of protons ( + ) & electrons
( – ) so the overall charge is zero (neutral)
Nucleus
o Center core containing protons and neutrons
o Has an overall positive charge
Electron cloud
o Area around nucleus which holds electrons in
different energy levels
o Has an overall negative charge
Characterizing Atoms
 Atomic Number = number of protons
o Determines the element you have
 Mass Number (Atomic Mass Number) = number of
protons and neutrons
 Atomic Mass = total averaged mass of protons &
neutrons in all types of an atom