Chapter 6: Periodic Table Trends Wasilla High School

Periodic Law Dmitri Mendeleev created the first real periodic table by arranging the elements in order or increasing atomic mass Was so accurate, he was able to predict the existence of elements not yet discovered Modern periodic table – elements are organized by increasing atomic number

Mendeleev’s Periodic Table

Periodic Trend #1: Atomic Size Atomic size increases from top to bottom and decreases from left to right

Periodic Trend #2: Ionization Energy The energy required to remove an electron from an atom You can have a first, second and third ionization energy Decreases as you move down a group, increases as you move across a period from left to right

Ionization Energy is Related To Valence Electrons Group IA elements have one valence electron Low 1st Ionization Energy Extremely High 2nd Ionization Energy Group IIA elements have two valence electrons Low 1st and 2nd Ionization Energy Extremely High 3rd Ionization Energy Nonmetals ALWAYS have high ionization energies They want to GAIN electrons not LOSE

Periodic Trend #3: Electronegativity Electronegativity is the ability of an atom to attract electrons Values decrease from top to bottom and increase from left to right