The Periodic Table

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 Similar properties based on the same number of valence electrons Numbered 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 Exceptions: 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 decreasing across a row

Electronegativity Ability of an atom to attract electrons to itself Increases across a row Decreases 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 Decreases down a column Increases 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 Atom gets smaller Anion – atom gains electron Atom gets bigger

Example of Ion Size

The Periodic Table