Which bond type is soluble in alcohol?
Metallic, ionic, polar covaletn, or nonpolar covalent bonds?
Which bond type has hard, brittle crystals?
(I think the second is ionic, but not positive.)
Polar covalent is more likely to be soluble in alcohol. I think you are right about the ionic crystals. They are hard and cleave along planes although I don't think they are necessarily brittle per se, at least the way I define brittle.
To determine which bond type is soluble in alcohol, we need to examine the nature of the bonds.
Ionic bonds: These bonds form between a metal and a non-metal. They involve a transfer of electrons from the metal to the non-metal, resulting in the formation of positively charged metal ions and negatively charged non-metal ions. Ionic compounds are generally soluble in polar solvents like water, but not necessarily in alcohol.
Polar covalent bonds: These bonds form between atoms that have different electronegativities. The sharing of electrons is unequal, resulting in a partial positive charge on one atom and a partial negative charge on the other. Polar covalent compounds are typically soluble in polar solvents such as water and alcohol.
Nonpolar covalent bonds: These bonds form between atoms that have similar electronegativities. The sharing of electrons is equal, resulting in no significant charge separation. Nonpolar covalent compounds are generally not soluble in polar solvents like water and alcohol.
Metallic bonds: These bonds occur between metal atoms and are characterized by the delocalization of electrons. Metallic compounds are not soluble in alcohol.
Therefore, the bond type that is soluble in alcohol is the polar covalent bond.
Regarding the bond type that has hard, brittle crystals, your intuition is correct. It is indeed the ionic bond. Ionic compounds tend to form crystalline structures that are hard and brittle. This is due to the strong electrostatic forces of attraction between the positive and negative ions in the crystal lattice.