Tour of the Periodic Table Honors chemistry

Main-Group Elements

• Elements in groups 1, 2, 13 – 18 • Alkali Metals (Group 1) • Alkaline Earth Metals (Group 2) • Halogens (Group 17) • Noble Gases (Group 18)

• Representative elements

• electron configurations are regular and consistent

• Valence electrons easy to write

• n = period • Group 1 and 2 → ns1 or ns2 • Group 13 – 18 (3A – 8A) → ns2 np(1-6)

Electron Configurations

Valence Electrons and Reactivity • Number of valence electrons (VE) determines reactivity of element

• Elements most “happy” when outermost shell has 8 electrons

• Elements gain or lose electrons in chemical reactions to get to 8.

• The fewer electrons gained or lost to get to 8, the more reactive it is.

• K has 1 VE, loses it to get to 8 in the next lower shell – very reactive!

• Cl has 7 VE, needs to gain 1 to get full 8 in outer shell – very reactive!

• O has 6 VE, needs to gain 2. Reactive, but not as much as Cl.

• Argon has 8 VE, full shell, not reactive at all!

Group 1: Alkali Metals (Li – Fr)

• Lithium (Li)

• Sodium (Na)

• Potassium (K)

• Rubidium (Rb)

• Cesium (Cs)

• Francium (Fr)

Group 1: Alkali Metals (Li – Fr) = metals that react with water to make akaline solutions

e.g. 2K + 2H2O H2 + 2KOH

• 1 valence electron very reactive

• Physical properties:

• Soft

• Shiny, but dulls quickly

• Good conductors of electricity

Group 2: Alkaline Earth Metals

• Beryllium (Be)

• Magnesium (Mg)

• Calcium (Ca)

• Strontium (Sr)

• Barium (Ba)

• Radium (Ra)

Group 2: Alkaline Earth Metals

• 2 valence electrons reactive, but less than alkali metals

• Properties:

• Harder than alkali metals

• Higher melting point than alkali metals

Transition Metals (Groups 3-12)

Transition Metals (Groups 3-12)

• D-block elements

• Variable outer electron configurations dependent on element they react with

• Less reactive than alkali and alkaline earth metals

• Physical properties:

• Ductile and malleable

• Good conductors of heat and electricity

Copper (Cu), silver (Ag), gold (Au) are in this group

Groups 13, 14, 15

• Boron (B) 3 valence electrons

• Carbon (C) 4 valence electrons

• Nitrogen (N) 5 valence electrons

Group 16: Chalcogens • Oxygen (O)

• Sulfur (S)

• Selenium (Se)

• Tellurium (Te)

• Polonium (Po)

• 6 valence electrons

• Biological function (nutrient or toxin)

Group 17: Halogens

A

Group 17: Halogens

• 7 valence electrons (ns2np5) most reactive group

• Like to react with alkali metals

• Physical properties:

• Wide range

• Liquid, solid and gas states

Group 18: Noble Gases

Group 18: Noble gases

• 8 valence electrons (ns2np6) unreactive

Hydrogen

• Most common element in universe 3 out of 4 atoms are H

• Consists of 1 proton and 1 electron

Lanthanides/Actinides

• 4f and 5f orbitals f-block of periodic table

• Actinides radioactive

• Shiny metals (like alkaline earth metals)

General Properties of Metals

• Most of the periodic table

• Properties:

• Excellent conductors

• Most are

• Ductile (= can be squeezed out into wire)

• Malleable (= can be hammered or rolled into sheets)

• A few are brittle (Mn, Bi)

Review Questions

• Which group of elements is most unreactive? Why?

• Noble gases; full valence level of electrons

• What properties do halogens have in common?

• 7 valence electrons, highly reactive, like to react with alkali metals to form salts

• Why is hydrogen a group by itself?

• 1 proton, 1 electron behaves differently

• Why are alkaline earth metals less reactive than alkali metals?

• Must lose 2 electrons; takes more energy