Radium (Ra)
Element 88 · alkaline earth metal · group 2, period 7
Radium is element 88, a alkaline earth metal in group 2 and period 7. Its electron configuration is [Rn] 7s2. That leaves 2 valence electrons in the outer shell, with the shells filling 2, 8, 18, 32, 18, 8, 2. Losing its 2 valence electrons is the shorter route to a full shell, so it carries a charge of +2.
- 88 protons
- 2 valence e−
- +2
- s-block
Radium Lewis dot structure
Radium has 2 valence electrons, so its Lewis symbol carries 2 dots: two single dots. The dots go one to a side before any of them pair up, so the unpaired ones show exactly how many bonds the atom tends to form. The ion has given those electrons away, which is why it is drawn in brackets with none.
Draw it in the Lewis structure generator →
Properties
| Atomic number | 88 |
|---|---|
| Symbol | Ra |
| Standard atomic weight | 226 u |
| Group | 2 |
| Period | 7 |
| Block | s-block |
| Category | alkaline earth metal |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s2 |
| Noble-gas notation | [Rn] 7s2 |
| Electrons per shell | 2, 8, 18, 32, 18, 8, 2 |
| Valence electrons | 2 |
| Common ionic charge | +2 |
| Electronegativity (Pauling) | 0.9 |
| Protons / electrons | 88 / 88 |
Electron configuration of radium
Orbitals fill from the lowest energy upward. Writing that out for radium gives 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s2, which is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s2 in plain text.
Everything up to Rn is the same as in that noble gas, so it is usually abbreviated to [Rn] 7s2. The part outside the bracket is what does the chemistry.
| Subshell | Electrons | Capacity |
|---|---|---|
| 1s | 2 | 2 |
| 2s | 2 | 2 |
| 2p | 6 | 6 |
| 3s | 2 | 2 |
| 3p | 6 | 6 |
| 3d | 10 | 10 |
| 4s | 2 | 2 |
| 4p | 6 | 6 |
| 4d | 10 | 10 |
| 4f | 14 | 14 |
| 5s | 2 | 2 |
| 5p | 6 | 6 |
| 5d | 10 | 10 |
| 6s | 2 | 2 |
| 6p | 6 | 6 |
| 7s | 2 | 2 |
Radium ion charge
Radium commonly forms ions with a charge of +2.
It has 2 valence electrons, so it is 6 short of a full octet and 2 above an empty outer shell. An atom takes whichever route is shorter, which is why the charge comes out as it does.
Common questions
What is the Lewis dot structure of radium?
The symbol Ra with 2 dots, one for each valence electron: two single dots. Dots go one to a side before any pair up, the same way electrons fill separate orbitals before sharing one. The Ra2+ ion is drawn in brackets with no dots, because it has lost them.
How many valence electrons does radium have?
Radium has 2 valence electrons. For groups 1 and 2 the count is the group number, and radium is in group 2.
What is the electron configuration of radium?
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s2, or [Rn] 7s2 written from the previous noble gas. Orbitals fill lowest energy first.
What is the charge of radium?
Radium commonly forms ions with a charge of +2. With 2 valence electrons it is 6 short of an octet and 2 above an empty shell, so it takes whichever route is shorter.
How many protons, electrons and neutrons does radium have?
A neutral radium atom has 88 protons and 88 electrons. Its standard atomic weight is 226, so the most common isotope has about 138 neutrons.
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