Francium (Fr)
Francium is element 87, an alkali metal in group 1, period 7. A neutral atom has 87 protons, 136 neutrons and 87 electrons, 1 of them valence electrons.
Alkali metal- Atomic number
- 87
- Atomic mass
- 223.02 u
- Valence electrons
- 1
- Protons · neutrons
- 87 · 136
- Electrons per shell
- 2, 8, 18, 32, 18, 8, 1
- At room temperature
- solid
Bohr model of francium
The Bohr model draws francium as a nucleus of 87 protons and 136 neutrons, with its 87 electrons on 7 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 32 in shell 4, 18 in shell 5, 8 in shell 6, 1 in shell 7. Press Build the atom to watch the shells fill from the inside out. The outer ring (the Q shell) is dashed: the electrons there are the ones that take part in chemistry.
Real electrons don't travel in neat circles. They live in fuzzy orbitals, shown below, but the Bohr picture is the quickest way to count shells and valence electrons.
Electron configuration of francium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s¹
Short form (noble gas notation): [Rn] 7s¹. The [Rn] stands for the electrons of radon, the noble gas before it.
How many valence electrons does francium have?
Francium has 1 valence electron.
Francium is in group 1, so it has 1 valence electron. It tends to lose that electron and form a +1 ion.
Protons, neutrons and electrons
| Protons | 87 | equal to the atomic number |
|---|---|---|
| Electrons | 87 | equal to the protons in a neutral atom |
| Neutrons | 136 | mass number 223 − 87 protons |
Atoms of the same element can have different numbers of neutrons (isotopes). The count above uses the rounded atomic mass, the way it's taught in class.
Francium properties
| Symbol | Fr |
|---|---|
| Category | Alkali metal |
| Group · period · block | 1 · 7 · s |
| Atomic mass | 223.02 u |
| State at 25 °C | solid |
| Melting point | 300 K (26.9 °C, 80.3 °F) |
| Boiling point | — |
| Density | — |
| Electronegativity (Pauling) | 0.7 |
| Atomic radius | 348 pm |
| First ionization energy | 3.9 eV |
| Electron affinity | 0.47 eV |
| Oxidation states | +1 |
| Common ion charge | +1 |
| Discovered | 1939 by Marguerite Perey |
Where francium sits on the periodic table
Group 1: Hydrogen, Lithium, Sodium, Potassium, Rubidium, Cesium.
Questions about francium
How many valence electrons does francium have?
Francium has 1 valence electron.
How many protons, neutrons and electrons does francium have?
A neutral francium atom has 87 protons and 87 electrons. Its most common form has about 136 neutrons (mass number 223 − 87 protons).
What is the electron configuration of francium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s¹, written in short form as [Rn] 7s¹.
What does the Bohr model of francium look like?
A nucleus of 87 protons and 136 neutrons, circled by 7 electron shells holding 2, 8, 18, 32, 18, 8, 1 electrons.
What is the atomic number of francium?
87. The atomic number is the number of protons in the nucleus, and it is what makes an atom francium.