The Chemical Basis of Life

Matter: anything that has mass and takes up space Atom: basic unit of matter Atomic # = # of protons (and electrons) Atomic mass = atomic # + # of neutrons Isotopes: atoms of the same element with different #’s of neutrons (different atomic weights)

# + atomic # = atomic weight Subatomic particles Particle Location Charge Mass Other Proton Nucleus + 1 Equal to atomic # Neutron # + atomic # = atomic weight Electron Outside nucleus - Usually = # of protons

Atoms are most stable when they have full outer “shells” 1st shell is full with 2, the rest with 8 When atoms share electrons to stabilize they form a covalent bond When atoms give up or gain electrons they become charged particles or ions Oppositely charged ions are attracted to one another in an ionic bond

Molecule: two or more atoms bonded together Compound: when atoms of different elements are combined