Table Flashcards
- Ionic Compounds
High melting/boiling points → Strong electrostatic forces between oppositely charged ions require large amounts of energy to break.
Solubility in water → Ionic compounds tend to dissolve in water as water’s polarity weakens ionic attractions, allowing dissolution.
Electrical conductivity (only in liquid or dissolved state) – Ions are mobile in molten or aqueous state but fixed in a solid lattice.
Hard but brittle – Rigid crystalline lattice structure makes them strong, but shifting layers of ions cause repulsion and shattering. Ionic solids break “shatter” rather than dent because their lattice structure doesn’t allow flexibility.
Ionic compounds are generally not soluble in nonpolar solvents like hexane because of the principle of “like dissolves like” – polar substances dissolve in polar solvents, and nonpolar substances dissolve in nonpolar solvents
- Covalent Molecular Compounds
Low melting and boiling points – Weak intermolecular forces (such as Van der Waals forces, dipole-dipole, or hydrogen bonding) require little energy to overcome.
Soft and flexible – Weak intermolecular forces allow molecules to move more freely. “crumbles or shatters”
Poor electrical conductivity – No free-moving charged particles to conduct electricity.
Solubility varies – Polar molecules dissolve in polar solvents (e.g., water), while nonpolar molecules dissolve in nonpolar solvents (e.g., hexane).
- Metallic Compounds
High melting/boiling points → Strong metallic bonds require a lot of energy to break.
Malleable (‘Dented’ or ‘Flattened’ in Hammer Test) → Metals can dent instead of shattering due to the Layers of atoms being able to slide over each other without breaking bonds.
Conductivity in solid (s) and liquid (l) states → – Delocalized electrons move freely, allowing heat and electricity to pass through.
Insoluble in water & hexane → No ions or polar regions to attract water; metallic bonding is too strong.
- Covalent Network Compounds
Extremely high melting/boiling points → Strong covalent bonds in a vast network.
Insoluble in water & hexane → No interaction with solvents.
Hard and brittle (‘Shattered’ or ‘Cracked’ in Hammer Test) → Covalent networks do not dent.
Usually non-conductive → No free electrons or ions, except in special cases (like graphite).
Solubility in Hexane – What It Tells Us
Key Rule:
Solubility in hexane suggests that a substance is nonpolar, because “like dissolves like” (hexane is a nonpolar solvent).
Solubility Patterns:
Covalent Molecular Compounds → Can dissolve in hexane if nonpolar.
Ionic Compounds & Covalent Network Solids → Do NOT dissolve in hexane because they are polar or have strong covalent bonding.
Metals → Do NOT dissolve in hexane (or in water).
How to know if substance is polar vs non polar
Solubility in water → Polar substances dissolve in water.
Solubility in hexane → Nonpolar substances dissolve in hexane.
Conductivity in aqueous solution → Suggests the presence of ions, meaning ionic (polar).
Polar substance
A polar molecule or compound has an unequal distribution of electrons, creating partial positive and negative charges.
Non polar substance
A nonpolar molecule has an equal sharing of electrons, meaning no charge separation.
Covelant Network usually non polar as it is a continous network with no charged regions.
Can metals be polar?
In metals, electrons are delocalized in a “sea of electrons,” meaning there are no fixed regions of partial positive or negative charge. Polarity arises from differences in electronegativity between bonded atoms, but in metals, atoms share electrons collectively rather than in directional bonds, preventing polarity.
How come if something is soluble in water it is polar?
Substances that are soluble in water are typically polar because their charged regions interact with the polar water molecules, allowing them to dissolve.
How do water molecules affect the solubility of ionic compounds?
Solubility in Water – Water’s polarity allows it to weaken ionic bonds. The negative ion is attracted to water’s positive hydrogen, and the positive ion to water’s negative oxygen. This pulls ions apart, breaking the lattice and allowing them to disperse in solution.
If something is polar what is it’s solubility in water?
A polar substance is generally soluble in water because water is also polar, following the principle “like dissolves like.”
