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Periodic Trends

Periodic Trends. Melting / Boiling Points Density Conductivity. Melting / Boiling Point Trends. Within Group 17 (VIIA) melting points and boiling points increase down the group. Boiling Points for Selected Elements (Room Temp ≈ 298 K). Melting / Boiling Point Trends.

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Periodic Trends

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  1. Periodic Trends Melting / Boiling Points Density Conductivity

  2. Melting / Boiling Point Trends • Within Group 17 (VIIA) melting points and boiling points increase down the group

  3. Boiling Points for Selected Elements(Room Temp ≈ 298 K)

  4. Melting / Boiling Point Trends • Within Group 17 (or VIIA) melting points and boiling points increase down the group • Fluorine & Chlorine – gases (room temp) • Bromine – liquid (room temp) • Iodine - solid (room temp) • In group 1 (IA), there is a decrease in melting point and boiling point going down the group

  5. Boiling Points for Selected Elements(Room Temp ≈ 298 K)

  6. Melting / Boiling Point Trends • Trends in melting points and boiling points are a measure of attractive forces between atoms (or molecules) • If bp/mp increases down a group, this indicates stronger attractive forces • If bp/mp decreases down a group, this indicates weaker attractive forces

  7. Melting / Boiling Point Trends • Moving left to right across a period, melting points: • Increase as the attractive forces change from metallic bonds with loosely held electrons to solids like carbon and silicon (which are complex network solids) • Different types of bonds, which we will discuss in more detail in later chapters

  8. Melting Points for Elements

  9. Melting / Boiling Point Trends • Moving left to right in a period, melting points: • Increase as the attractive forces change from metallic bonds with loosely held electrons to solids like carbon and silicon where outer electrons are tied up in a complex network • Different types of bonds, which we will discuss in more detail in later chapters • Melting points then drop off sharply for non-metals, which have very weak forces of attraction

  10. Melting Points for Elements

  11. Density Trends • Densities of elements increase down a group as atomic number increases

  12. Density Trends

  13. Density Trends • Densities of elements increase down a group as atomic number increases • Across periods (left → right), densities increase, then decrease • Elements with the greatest densities are at the center of period 6.

  14. Density Trends

  15. Trends in Conductivity • All metals are good conductors of heat and electricity. • The best conductors are (in this order): • Ag>Cu>Au>Al>Ca>Na>Mg • Non-metals are non-conductors

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