Ch. 6 The Periodic Table

Mendeleev’s Periodic Table Elements in the periodic table are arranged by repeating properties Arranged in order by increasing atomic mass Left spaces where he predicted future elements would fit

Mendeleev’s Periodic Table

Periodic Law In the modern periodic table, elements are arranged in order by increasing Atomic Number 7 horizontal rows called periods Each period corresponds to a principle energy level Elements within a column (group) have similar properties

Periodic Law States: when elements are arranged by increasing atomic number, there is a periodic repetition of their physical and chemical properties

Metals, Nonmetals, Metalloids

Metals 80% of the periodic table is metals Good conductors of heat and electricity Malleable- can be shaped Ductile- can be drawn into wires Lustrous Solids at room temperature (except Hg)

Nonmetals Poor conductors of heat and electricity Not malleable Not ductile dull

Metalloids Generally has some properties of a metal, some of a nonmetal

Lithium (Li) Sodium (Na) Potassium (K) Alkali Metals 1s22s1 1s22s22p63s1 Potassium (K) 1s22s22p63s23p64s1

Alkaline Earth Metals Beryllium (Be) 1s22s2 Magnesium (Mg) 1s22s22p63s2 Calcium (Ca) 1s22s22p63s23p64s2

Halogens Fluorine (F) 1s22s22p5 Chlorine (Cl) 1s22s22p63s23p5 Bromine (Br) 1s22s22p63s23p64s23d104p5

Noble Gasses 1s22s22p6 1s22s22p63s23p6 1s22s22p63s23p64s23d104p6 Neon (N) 1s22s22p6 Argon (Ar) 1s22s22p63s23p6 Krypton (Kr) 1s22s22p63s23p64s23d104p6

Trends in Atomic Size Atomic radius is ½ the distance between the nuclei of 2 like atoms As you move DOWN a group, atomic size increases As you move LEFT to RIGHT across a period size decreases

Why? As you move across the period you gain electrons but you also gain protons. More + protons hold their electrons tighter As you move down the group you gain more electrons which are in electron orbitals further away from the nucleus. The nucleus has less influence the further out you move.

Trends in Ionization Energy Ionization Energy is the energy required to remove 1 electron from a gaseous atom As you move DOWN a group ionization energy DECREASES As you move LEFT to RIGHT across a period ionization energy INCREASES

Why?

Trends in Electronegativity Electronegativity is the tendency of an atom to attract electrons in a compound As you move DOWN a group Electronegativity DECREASES As you move LEFT TO RIGHT across a period Electronegativity INCREASES

Summary of Periodic Trends