Which of the following properly describes an ion?

an atom that has lost or gained one or more neutrons
an atom or molecule that has lost or gained one or more electrons
an atom or molecule that has lost or gained one or more protons
a molecule that has lost or gained one or more atoms
d?

The correct answer is: an atom or molecule that has lost or gained one or more electrons.

To check which choice properly describes an ion, it is important to understand what an ion is. An ion is an atom or molecule that has an unequal number of protons and electrons, resulting in a net electrical charge. This imbalance in charge is due to the loss or gain of one or more electrons.

Now let's examine each option:

a) "an atom that has lost or gained one or more neutrons": This description doesn't accurately define an ion. Neutrons have no charge, so the gain or loss of neutrons wouldn't result in an electrical charge.

b) "an atom or molecule that has lost or gained one or more electrons": This is the correct answer. As mentioned earlier, ions result from the gain or loss of electrons, which leads to an unequal number of protons and electrons.

c) "an atom or molecule that has lost or gained one or more protons": This option is incorrect. While protons are involved in determining the overall charge of an atom, the gain or loss of protons changes the element's identity, rather than creating an ion.

d) "a molecule that has lost or gained one or more atoms": This option is not an accurate description of an ion. Ions are formed due to the gain or loss of electrons, not atoms.

Therefore, the correct answer is b) "an atom or molecule that has lost or gained one or more electrons."