Atoms and Ions - Sept 13, 2024

How Do Atoms and Ions Differ?

  • An ion is an atom or group of atoms that has an electrical charge, either positive or negative.

  • Atoms have an equal number of protons and electrons and so do not have an overall charge.

  • Atoms with incomplete outer electron shells are unstable. By either gaining or losing electrons, atoms can obtain full outer electron shells and become stable.

  • When this happens, atoms have an unequal number of protons and electrons and so have an overall charge. This is how atoms become ions.

Positive and Negative Ions:

  • The electrons in the outermost shells are called valence electrons.

  • These electrons can be either lost or gained in order to have a full outer shell like the stable noble gases.

  • The electron configuration of an atom shows how many electrons it must lose or gain to have a filled outer shell.

  • Atoms with a nearly empty outer shell (1, 2, or 3 valence electrons) will lose electrons to obtain a full outer shell.

  • Atoms with a nearly full outer shell (5, 6, or 7 valence electrons), will gain electrons to obtain a full outer shell.

Cations and Anions:

  • An atom that has lost electrons will have a positive charge, called a cation (more protons than electrons).

  • An atom that has gained electrons will have a negative charge, called an anion (more electrons than protons).

  • In order for a compound to be stable, it must have a completely filled outer electron shell- aka (stable octet)

Metals:

  • Tend to have 1, 2, or 3 electrons in the outer orbits (shells)

  • They lose electrons when they combine with other elements to form positive ions (cations) : note the t i n the word think +

  • They lose electrons, thus they have the same electron arrangement as the Noble gas a row above them.

  • Lithium atom 2, 1 = lithium ion (2) = Li+

  • Magnesium Atom 2, 8, 2 = magnesium ion (2,8) = mg2+

Non-metals:

  • Non-metals - tend to have 4, 5, 6, or 7 electrons in their outer orbits (shells).

  • They gain electrons to form negative ions (anions)

  • They gain electrons, thus they have the same electron arrangement as the Noble gas in the same row.

    • Negative ions have a small “-” symbol and a number by this to indicate how many electrons have been gained to fill their outer shell.