2.2.5 Structures of ionic compounds Flashcards
are electrostatic bonds in ionic compounds strong or weak?
strong
why is a large amount of energy needed to break ionic bonds?
because of strong electrostatic forces of attraction
why do ionic compounds have high melting and boiling points?
because of the large amount of energy needed to break strong electrostatic forces of attraction that hold oppositely charged ions together in the solid lattice
what is the correlation of charge and strength of electrostatic forces between ions?
the greater the charge on the ions, the stronger the electrostatic forces of attraction between them (tf more E needed to break bonds)
which has a higher melting point? MgO (Mg^2+ and O^2-)
or NaCl (Na^- and Cl^-)
MgO
the greater the charge, the …..charge density of the ions?
greater
do ionic compounds have delocalised electrons?
NO that is metals and graphite
why are ionic compounds brittle?
due to the strong electrostatic forces of attraction, the bonds create crystals in rigid, lattice structures. Applying pressure shifts the alignment of the ions (surrounded by oppositely charged ions, shifting will cause ions to repel) and results in brittleness.
why are ionic compounds soluble in water?
charged ions interact with polar water molecules (which disrupts the lattice)
what are the two main factors which solubility depends on?
-breaking down the ionic lattice
-the polar molecules attracting and surrounding ions
what will many ionic compounds dissolve in?
in polar solvents eg water
what does the δ+ end of the polar molecule surround?
the δ+ end of the polar molecule can surround the negative anion
what does the δ- end of the polar molecule surround?
the δ- end of the polar molecule can surround the positive cation
explain the two main factors that solubility depends on
-the solubility of an ionic compound depends on :
-the relative strength of the electrostatic forces of attraction within the ionic lattice
-the attractions between the ions and the polar molecule
what is the general rule for solubility?
the greater the ionic charge the less soluble an ionic compound is (MANY exceptions)
when can ionic compounds conduct electricity?
when molten and aqueous, never when solid
why can ionic compounds not conduct electricity as a solid?
because the ions are in fixed positions within the solid lattice so there are no mobile charge carriers
why can ionic compounds conduct electricity molten or aqueous?
because the ions are no longer in fixed positions as the lattice has broken down, therefore, the ions are free to act as mobile charge carriers
