Question

now, lets take a look at another molecule to determine if it will dissolve in water. in other words, will water molecules form a hydration sphere around this molecule?
the molecule on the right is iodine (i₂). it is found in foods, such as seaweed, and is required by the human body, especially the thyroid gland.
why do you think iodine is insoluble in water?
iodine is a positive ion, so it wont dissolve in water.
iodine is a negative ion, so it wont dissolve in water.
iodine has both a full positive charge and a full negative charge, so it will not dissolve in water.
iodine is held together with strong covalent bonds and lacks any significantly charged regions. the interactions between water and iodine are not strong enough to overcome these covalent bonds.
molecules of iodine are made up of more than one atom.

Explanation:

Water is a polar molecule. For a substance to dissolve in water, it should have some polarity or charged regions so that water molecules can interact with it (through hydrogen - bonding or ion - dipole interactions). Iodine (\(I_2\)) is a non - polar molecule. It has a covalent bond where electrons are shared equally (as given in the hint: "They share electrons equally and are not charged"). The non - polar nature of \(I_2\) means that the interactions between non - polar \(I_2\) and polar water molecules (which are mainly London dispersion forces in the case of \(I_2 - water\) interaction) are not strong enough to break the covalent bonds within the \(I_2\) molecule and also overcome the hydrogen - bonding in water.

Answer:

Iodine is held together with strong covalent bonds and lacks any significantly charged regions. The interactions between water and iodine are not strong enough to overcome these covalent bonds.