Periodic Trends in Melting and Boiling Points

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A level Chemistry (3.1 The Periodic Table) Karteikarten am Periodic Trends in Melting and Boiling Points, erstellt von Yinka F am 03/03/2018.
Yinka F
Karteikarten von Yinka F, aktualisiert more than 1 year ago
Yinka F
Erstellt von Yinka F vor mehr als 6 Jahre
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Zusammenfassung der Ressource

Frage Antworten
Describe the trend in melting/boiling points of Period 2 and 3 elements The melting/boiling points of the Period 2 and 3 elements generally increase from the first to the fourth elements in the period, but then decrease from the fourth to the eighth elements
Name the metals in Period 2 and 3 PERIOD 2 = Li, Be PERIOD 3 = Na, Mg, Al
Describe and explain the melting and boiling points for the metals For the metals (Li, Be, Na, Mg and Al) melting/boiling points increase across the period because the metal-metal bonds get stronger. The bonds get stronger because the metal ions have... 1. A greater charge 2. An increasing number of delocalised electrons 3. A decreasing ionic radius This leads to a higher charge density, which attracts the ions together more strongly
Name the elements with giant covalent structures in Period 2 and 3 PERIOD 2 = B, C PERIOD 3 = Si
Describe and explain the melting and boiling points for the giant covalent structures The elements with giant covalent structures (B, C and Si) have strong covalent bonds linking all their atoms together. A lot of energy is needed to break these bonds, therefore they have the highest melting/boiling points in their periods
Name the elements with simple covalent structures in Period 2 and 3 PERIOD 2 = N, O, F (,Ne) PERIOD 3 = P, S, Cl (,Ar)
Describe and explain the melting and boiling points for the simple covalent structures The covalent bonds between the atoms in a molecule are very strong but the melting/boiling points depend upon the strength of the London forces between their molecules. These forces are weak and easily overcome. More atoms in a molecule mean stronger London forces. E.g. in Period 3, sulfur (S₈) is the biggest molecule so it has a higher melting and boiling point than P₄ or Cl₂
Describe and explain the melting and boiling points for the noble gases The noble gases have the lowest melting and boiling points because they exist as individual atoms (they're monatomic), resulting in very weak London forces
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