• First to organize elements in a table based on atomic mass & chemical properties.
• Used properties as first property, then mass.
• Left spaces for elements not yet discovered.

• Also called "main group elements"
• Wide range of phys. & chem. prop.
• Elements in "A" groups
• Same number of valence elecrons as their "A" group.
• Hve electron configs w/ their highest "s" orbital filled and partially filled "p" orbitals. Some have filled d orbitals in the next lower level.
• Reactive enough that they're often found as part of compounds

• Group 8A
• All have their highest "s" or "s" and "p" orbitals filled.
• Very unreactive; not usually found as part of a compound. Also, called the "inert gases".

• Group 1A, except hydrogen - all have 1 valence electron
• Extremely reactive - not normally found as free elements in nature; usually part of a compound.

• Group 2A - all have 2 valence electrons
• Less reactive than alkali metals, but still too reactive to normally be found as free elements in nature.

• Group 7A - all are nonmetals that have 7 valence electrons 
• One electron short of a noble gas configuration - makes them very reactive.

• Has a 1s^1 config. like an alkali metal, but it's a nonmetal.
• Like an alkali metal it is extremely reactive, but it forms compounds differently.

• Has a 1s^2 like an alkaline earth metal, but it's a nonmetal.
• Alkaline earth metals are very reactive; helium is a nonreactive noble gas (its highest energy level is filled).

• Have typical metallic properties
• Have electrons in their highest s orbital and next d orbital
• less reactive than group 1A and 2A metals
• Some are very unreactive and can be found as free elements in nature.

• f block
• Electrons in highest s orbital and a nearby f orbital
• the lanthanides are shiny metals similar in reactivity to the alkaline earth metals.
• The actinides are all radioactive & most of the, are synthetic

• Energy needed to remove an electron from an atom
• Thhe trends are due to differences in the attraction of the outer electrons to the nucleus as the number of protons and amount of shielding change.

Ions are smaller or larger than their original atoms due to unbalanced charged and, sometimes, the loss or gain of an entire orbital.

A cation has a SMALLER radius than its original atom because it lost electrons.

An anion has a LARGER radius than its original atom because it gained electrons.

The general trends got ionic radius are the same as for atomic radius for the same reasons