Why do metals have a high melting and boiling point?

Metallic bonding is the strong attraction between closely packed positive metal ions and a 'sea' of delocalised electrons. The attraction between the metal ions and the delocalised electrons must be overcome to melt or to boil a metal. These attractive forces are strong, so metals have high melting and boiling points.
A.

Why is the melting point of magnesium higher than that of sodium?

The nuclear charge of magnesium is higher than that of sodium. Magnesium has more electrons than sodium. Both these mean that there is a stronger electrostatic attraction between the positive magnesium ions and its delocalised electrons in the giant metallic lattice. Therefore more energy is required to overcome it.
  • Why aluminum oxide has a high melting point?

    The giant structures (the metal oxides and silicon dioxide) will have high melting and boiling points because a lot of energy is needed to break the strong bonds (ionic or covalent) operating in three dimensions. These oxides tend to be gases, liquids or low melting point solids.
  • Why silicon dioxide has a high melting point?

    Silicon dioxide is very hard. It has a very high melting point (1,610 °C) and boiling point (2,230 °C), is insoluble in water, and does not conduct electricity. These properties result from the very strong covalent bonds that hold the silicon and oxygen atoms in the giant covalent structure.
  • Why does chlorine have a very low boiling point?

    Chlorine, as chlorine has fewer electrons shells than bromine. As a result, chlorine is smaller and has a smaller atomic radius. The difference in size, relates to boiling point of the molecule. This is because the <strong>size effects the strength of the forces between the molecules</strong> (intermolecular forces).
B.

Why do ionic compounds have a high melting point?

High melting and boiling points - Ionic bonds are very strong - a lot of energy is needed to break them. So ionic compounds have high melting and boiling points. Conductive when liquid - Ions are charged particles, but ionic compounds can only conduct electricity if their ions are free to move.
  • Why do ionic compounds have a high melting point?

    High melting and boiling points - Ionic bonds are very strong - a lot of energy is needed to break them. So ionic compounds have high melting and boiling points. Conductive when liquid - Ions are charged particles, but ionic compounds can only conduct electricity if their ions are free to move.
  • Do molecular compounds have a high melting point?

    Molecular substances tend to be gases, liquids or low melting point solids, because the intermolecular forces of attraction are comparatively weak. You don't have to break any covalent bonds in order to melt or boil a molecular substance.
  • Why do ionic compounds conduct electric current when they are melted or dissolved in water?

    Conductive when liquid - ions are charged particles, but ionic compounds can only conduct electricity if their ions are free to move. So ionic compounds do not conduct electricity when they are solid, but they do conduct electricity when they are dissolved in water or when they are melted.
C.

Why is the melting point of sodium chloride high?

Sodium chloride has a high melting and boiling point. There are strong electrostatic attractions between the positive and negative ions, and it takes a lot of heat energy to overcome them. Ionic substances all have high melting and boiling points.
  • Why silicon dioxide has a high melting point?

    Silicon dioxide is very hard. It has a very high melting point (1,610 °C) and boiling point (2,230 °C), is insoluble in water, and does not conduct electricity. These properties result from the very strong covalent bonds that hold the silicon and oxygen atoms in the giant covalent structure.
  • Why does sodium have a low melting point?

    Melting and boiling points rise across the three metals because of the increasing strength of the metallic bonds. The number of electrons which each atom can contribute to the delocalised "sea of electrons" increases. The atoms also get smaller and have more protons as you go from sodium to magnesium to aluminium.
  • Why does a diamond have a high melting point?

    Each carbon atom is covalently bonded to four other carbon atoms. A lot of energy is needed to separate the atoms in diamond. This is because covalent bonds are strong, and diamond contains very many covalent bonds. This makes diamond's melting point and boiling point very high.

Updated: 2nd October 2019

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