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 FamilyoSimilar 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 stabilityoExceptions: 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

itselfoIncreases 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

electronoDecreases down a column

oIncreases across a row

Think about Corners

Practice- Circle your answer

choiceLarger 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 electronoAtom gets smaller

●Anion – atom gains electronoAtom gets bigger

Exampl

e

of Ion

Size