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This chapter explores the periodic properties of elements, tracing the development of the periodic table from Mendeleev (1869) to Moseley (1913). It discusses electron shells, atomic radii, ionization energy, and electron affinities, highlighting periodic trends. The characteristics of metals, nonmetals, and metalloids are detailed, along with the trends in reactivity among active metals in Groups 1 and 2. The chapter also covers the flame colors of reactive metals and provides insights into the behaviors of noble gases and halogens.
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Chapter 7 Periodic Properties of the Elements
Development of the Periodic Table • Mendeleev – 1869 • Moseley - 1913
Electron Shells and Sizes of Atoms • Electron Shell = Energy Level • Atomic Radii • Increase top to bottom • Decrease left to right
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
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
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
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
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
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
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
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
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
Group 8A: Noble Gases • Gases • Nonmetals • Monoatomic • Extremely nonreactive • Xenon will react with fluorine to form XeF2, XeF4, and XeF6 • Krypton forms KrF2
