1. Periodic Properties of the Elements
Chapter 7
Periodic Properties of the Elements

2. Development of the Periodic Table
Mendeleev – 1869
Moseley

3. Electron Shells and Sizes of Atoms
Electron Shell = Energy Level
Atomic Radii
Increase top to bottom
Decrease left to right

4. Ionization Energy
Energy required to remove an electron from the ground state of a gaseous atom/ion
First – Second – Third : increases
Periodic Trend
Decreases top to bottom
Increases left to right
Representative elements have greater IE than transition metals

5. Electron Affinities
Energy change that occurs when an electron is added to one atom of the element in the gaseous state
“ how easy an element gains electrons”
Trend
Becomes less negative from top to bottom
Becomes more negative from left to right
Noble Gases ΔE > 0

6. Metals, Nonmetals, and Metalloids
Approx. 78% Metals, 15% Nonmetals, 7% Metalloids
Metallic properties
Shiny luster, conduct heat/electricity, malleable, ductile, solids at room temp., low IE, lose electrons in chem. Rxn, transition metals form more than one cation
Nonmetallic properties
Non-lustrous, poor conductors of heat/electricity, low melting points, many are diatomic, tend to gain electrons
Metalloid
Some like metals-some like nonmetals, some are semi-conductors

7. Group Trends for Active Metals: Group 1 Alkali Metals
General Properties
Soft metals
Silvery, metallic luster
high thermal/electrical conductivity
low density/melting point (increase as you move down group)
very reactive metals
+1 ions
colored flames
Reactions
M + Water = metal hydroxide + hydrogen
M + Oxygen = metal oxides, peroxides, superoxides

8. Group Trends for Active Metals: Group 2 Alkaline Earth Metals
General Properties
Solids with typical metallic properties
Harder, more dense, higher melting points as compared to Group 1
Less reactive than Group 1; reactivity increases top to bottom
2+ ions
Form colorless or white compounds
Colored flames

9. Flame Color – Reactive Metals
Group 1
Lithium – Crimson Red
Sodium – Yellow
Potassium – Blue-Violet
Rubidium – Pinkish Violet
Cesium – Pinkish Violet
Group 2
Calcium – Yellowish Brick Red
Strontium – Deep Dark Red
Barium – Yellow-green

10. Hydrogen Colorless diatomic gas Insoluble in water
Lightest of all gases
Three isotopes
1H, 2H, 3H
Burns in air to form water
(not highly reactive)
Reacts with nonmetals to form molecular compounds
Reacts with metals to form metallic hydrides

11. Group 6A: Oxygen Group
Group changes from nonmetal gas to metalloids to metal
Oxygen found naturally in two forms – O2 and O3
Sulfur forms several allotropes

12. Group 7A: Halogens Name means “salt formers”
Exist in all three states (g, l, s)
Elements are colored
Fluorine – pale yellow
Chlorine – green
Bromine – reddish brown
Iodine – grayish black solid; violet vapor
Typically irritating to skin
Forms -1 ions
Reactivity decreases down the group

13. Group 8A: Noble Gases Gases Nonmetals Monoatomic Extremely nonreactive
Xenon will react with fluorine to form XeF2, XeF4, and XeF6
Krypton forms KrF2