Periodic Properties of the Elements

1. Chapter 7 Periodic Properties of the Elements

2. Development of the Periodic Table • Mendeleev – 1869 • Moseley - 1913

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