Chemistry Unit 3

Lavoisier

Divided elements into metals/nonmetals

Dobereiner

Created triads (groups of 3 similar elements)

Newlands

Developed Law of Octaves (repeating pattern of 8)

Meyer

Arranged elements by valence (combining power)

Mendeleev

Arranged by atomic mass,

Predicted properties of undiscovered elements

Mosely

Rearranged table based on atomic numbers

Seaborg

Pulled out lanthanide/actinide series

Periods

Horizontal rows (1-7),

Period # tells energy level of highest energy electrons

Families/Groups

Vertical columns

Arranged based on similarities in reactivity

1A-8A correspond to valence electrons

Metals

Left of zigzag line

Luster, Malleable, Conductors, Ductile, mainly SOLID

Metallic oxides react w water to form BASES

Nonmetals

Right of zigzag line

Gases, Brittle solids, insulators

Nonmetallic oxides react w water to form ACIDS

Metalloids

Touches zigzag line (NOT ALUMINUM)

Properties of both metals and nonmetals

Semiconductors

Akali Metals

Group 1A

Extremely reactive- explosive in water

NOT found alone in nature, soft

Alkaline Earth Metals

Group 2A

Same as Alkali but less(?)

Transition

Group 1B-8B (3-12)

Properties differ from each other (wide variety)

Many form COLORED solutions

Halogens

Group 7A

Very REACTIVE nonmetals

DIATOMIC (2 atoms combine w each other)

Noble Gases

Group 8A

INERY (NO REACT)

Periodic Trend: Atomic Radii

“Size of atom”

INCREASES going DOWN due to addition of new energy levels

DECREASES going ACROSS a period due to increase in nuclear charge (# of protons) pulling electrons, greater attractive force

Periodic Trend: Ionization Energy

Energy to remove an electron from a gaseous atom

DECREASE going DOWN a family cs bigger size = less attractive force + shielding by inner electrons

INCREASE going ACROSS period cs increased nuclear charge = more attractive force

Formation of Ions

Atoms gain/ lose elctrons to have perfect noble gas config

Metals: lose electrons = positive ions

Nonmetals: gain electrons = negative ions

Ion Atomic Radius

Positive Ions are smaller than OG

Negative Ions are larger than OG

Electronegativity

Attraction for elcttrons w/o a bond

Trends same as ionization energy

Electron Affitinity

Attraction for electrons X bond)

Same trend as electronegativity

Periodic Trend: Melting Point

DECREASES DOWN metal roups

INCREASES UP nonemtal groups

INCREASES ACROSS period until GROUP 4A then DECREASE

Reactivity

INCREASES DOWN a family for METALS

DECREASES DOWN for a family of NONMETALS

Density

INCREASES DOWN a family