The Periodic Table
Chapter 5 Notes
Mendeleev
●Designed first periodic table (1869)
●Arranged mostly by increasing atomic
mass
●Elements in the same column have similar
properties
Moseley
●Arranged by increasing atomic number
Periodic Law
●Elements’ physical and chemical
properties show a periodic [“repeating”]
pattern when arranged by atomic number
●COLUMN = Group or Family
oSimilar properties based on the same number
of valence electrons
oNumbered 1-18 or with Roman numerals
●ROW = Period
Valence electrons
●Electrons in the outermost shell
●Octet Rule = all atoms want 8 valence
electrons to achieve stability
oExceptions: H, He
Families of the Periodic Table
Alkali Metals
●Soft
●Most reactive metals
Noble Gases
●very UNreactive
●“inert”
Halogens
●Most reactive nonmetals
Metals
●luster/shiny, good conductors of heat &
electricity, malleable, ductile
●LEFT SIDE of periodic table
Nonmetals
●not shiny, poor conductors, not malleable
or ductile, brittle
●RIGHT SIDE of periodic table
Metalloids
●“semi-metals”
●some properties of metals, some of
nonmetals
●touch ZIG-ZAG LINE
Periodic Trends
Atomic Radius
●Distance from the nucleus to the outer
electrons
●Decreases across a row
●Increases down a column
Explanation of Atomic Radius
increasing down a column
Explanation of
Atomic Radius
increasing
down
a column
Explanation of Atomic Radius
decreasing across a row
Explanation of Atomic Radius
decreasing across a row
Electronegativity
●Ability of an atom to attract electrons to
itself
oIncreases across a row
oDecreases down a column
Ionization Energy
●Energy needed to remove an electron
●Increases across a row
●Decreases down a column
Electron Affinity
●How much an atom wants to gain an
electron
oDecreases down a column
oIncreases across a row
Think about Corners
Practice- Circle your answer
choice
Larger atomic radius?
1) Mg or Sr
2) Mg or S
Larger electronegativity?
3) P or Sb
4) Ge or Br
Larger ionization energy?
5) Ca or Se
6) Ca or Ra
Ion Size
●Cation – atom loses electron
oAtom gets smaller
●Anion – atom gains electron
oAtom gets bigger
Exampl
e
of Ion
Size