Periodic table charges
The charge an element takes when it forms an ion, and the valence electron count that decides it.
An atom forms an ion by taking the shortest route to a full outer shell. An element with one or two valence electrons loses them; one that is one or two short gains instead. That is why group 1 is always +1, group 2 is +2, group 16 is −2 and group 17 is −1 - the charge is the group position, read as a distance from a full shell. The transition metals sit in the middle with several routes open to them, which is why they have more than one charge each.
Main-group charges
These follow from the group number alone. Lose the valence electrons, or gain enough to finish the octet, whichever is fewer.
| Element | Group | Valence e− | Short of octet | Charge |
|---|---|---|---|---|
| H Hydrogen | 1 | 1 | 7 | +1, -1 |
| He Helium | 18 | 2 | 6 | none |
| Li Lithium | 1 | 1 | 7 | +1 |
| Be Beryllium | 2 | 2 | 6 | +2 |
| B Boron | 13 | 3 | 5 | +3 |
| C Carbon | 14 | 4 | 4 | +4, -4 |
| N Nitrogen | 15 | 5 | 3 | -3 |
| O Oxygen | 16 | 6 | 2 | -2 |
| F Fluorine | 17 | 7 | 1 | -1 |
| Ne Neon | 18 | 8 | full | none |
| Na Sodium | 1 | 1 | 7 | +1 |
| Mg Magnesium | 2 | 2 | 6 | +2 |
| Al Aluminium | 13 | 3 | 5 | +3 |
| Si Silicon | 14 | 4 | 4 | +4 |
| P Phosphorus | 15 | 5 | 3 | -3 |
| S Sulfur | 16 | 6 | 2 | -2 |
| Cl Chlorine | 17 | 7 | 1 | -1 |
| Ar Argon | 18 | 8 | full | none |
| K Potassium | 1 | 1 | 7 | +1 |
| Ca Calcium | 2 | 2 | 6 | +2 |
| Ga Gallium | 13 | 3 | 5 | +3 |
| Ge Germanium | 14 | 4 | 4 | +4 |
| As Arsenic | 15 | 5 | 3 | +3, +5, -3 |
| Se Selenium | 16 | 6 | 2 | -2, +4, +6 |
| Br Bromine | 17 | 7 | 1 | -1 |
| Kr Krypton | 18 | 8 | full | none |
| Rb Rubidium | 1 | 1 | 7 | +1 |
| Sr Strontium | 2 | 2 | 6 | +2 |
| In Indium | 13 | 3 | 5 | +3, +1 |
| Sn Tin | 14 | 4 | 4 | +2, +4 |
| Sb Antimony | 15 | 5 | 3 | +3, +5 |
| Te Tellurium | 16 | 6 | 2 | -2, +4, +6 |
| I Iodine | 17 | 7 | 1 | -1 |
| Xe Xenon | 18 | 8 | full | none |
| Cs Caesium | 1 | 1 | 7 | +1 |
| Ba Barium | 2 | 2 | 6 | +2 |
| Tl Thallium | 13 | 3 | 5 | +1, +3 |
| Pb Lead | 14 | 4 | 4 | +2, +4 |
| Bi Bismuth | 15 | 5 | 3 | +3 |
| Po Polonium | 16 | 6 | 2 | +4, +2 |
| At Astatine | 17 | 7 | 1 | -1 |
| Rn Radon | 18 | 8 | full | none |
| Fr Francium | 1 | 1 | 7 | +1 |
| Ra Radium | 2 | 2 | 6 | +2 |
| Nh Nihonium | 13 | 3 | 5 | +3 |
| Fl Flerovium | 14 | 4 | 4 | +4 |
| Mc Moscovium | 15 | 5 | 3 | -3 |
| Lv Livermorium | 16 | 6 | 2 | -2 |
| Ts Tennessine | 17 | 7 | 1 | -1 |
| Og Oganesson | 18 | 8 | full | none |
Transition metal charges
These are not derivable from the group. A transition metal can give up electrons from both its outer s subshell and the d subshell underneath, and several of those states are stable enough to be common, so each one is listed rather than calculated. The first charge shown is the one you meet most often.
| Element | Group | Common charges | Most common |
|---|---|---|---|
| Sc Scandium | 3 | +3 | +3 |
| Ti Titanium | 4 | +4, +3 | +4 |
| V Vanadium | 5 | +5, +4, +3, +2 | +5 |
| Cr Chromium | 6 | +3, +6, +2 | +3 |
| Mn Manganese | 7 | +2, +4, +7 | +2 |
| Fe Iron | 8 | +3, +2 | +3 |
| Co Cobalt | 9 | +2, +3 | +2 |
| Ni Nickel | 10 | +2 | +2 |
| Cu Copper | 11 | +2, +1 | +2 |
| Zn Zinc | 12 | +2 | +2 |
| Y Yttrium | 3 | +3 | +3 |
| Zr Zirconium | 4 | +4 | +4 |
| Nb Niobium | 5 | +5 | +5 |
| Mo Molybdenum | 6 | +6, +4 | +6 |
| Tc Technetium | 7 | +7 | +7 |
| Ru Ruthenium | 8 | +3, +4 | +3 |
| Rh Rhodium | 9 | +3 | +3 |
| Pd Palladium | 10 | +2, +4 | +2 |
| Ag Silver | 11 | +1 | +1 |
| Cd Cadmium | 12 | +2 | +2 |
| Hf Hafnium | 4 | +4 | +4 |
| Ta Tantalum | 5 | +5 | +5 |
| W Tungsten | 6 | +6, +4 | +6 |
| Re Rhenium | 7 | +7, +4 | +7 |
| Os Osmium | 8 | +4 | +4 |
| Ir Iridium | 9 | +4, +3 | +4 |
| Pt Platinum | 10 | +4, +2 | +4 |
| Au Gold | 11 | +3, +1 | +3 |
| Hg Mercury | 12 | +2, +1 | +2 |
| Rf Rutherfordium | 4 | none | — |
| Db Dubnium | 5 | none | — |
| Sg Seaborgium | 6 | none | — |
| Bh Bohrium | 7 | none | — |
| Hs Hassium | 8 | none | — |
| Mt Meitnerium | 9 | none | — |
| Ds Darmstadtium | 10 | none | — |
| Rg Roentgenium | 11 | none | — |
| Cn Copernicium | 12 | none | — |
How to read a charge off the table
Find the group
Count the columns. Group 1 is the far left, group 18 the far right.
Get the valence electrons
Groups 1 and 2 have that many. Groups 13 to 18 have the group number minus 10.
Take the shorter route
Fewer than four valence electrons, and losing them is shorter, so the charge is positive and equal to the count. More than four, and gaining is shorter, so the charge is negative and equal to eight minus the count.
Check group 18
A full outer shell has no shorter route, so the noble gases form no ions.