Étain (Sn): Bohr Model, Protons, Neutrons & Electrons
Étain is element number 50, a post-transition metal in group 14, period 5. Its atom has 50 protons, 70 neutrons and 50 electrons arranged in 5 shells: 2, 8, 18, 18, 4.
- 50 protons
- 70 neutrons
- 50 electrons
Protons, neutrons and electrons in tin
Le atomic number of tin is 50, so every tin atom has 50 protons. A neutral atom has the same number of electrons, 50. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For tin-120, that is 120 − 50 = 70 neutrons. Tin has 10 stable isotopes, with 62, 64, 65, 66, 67, 68, 69, 70, 72, 74 neutrons.
How to draw the Bohr model of tin
- Draw the nucleus and write 50 p⁺ et 70 n⁰ inside it.
- Draw the first shell and put 2 electrons on it (the first shell holds at most 2).
- Draw the second shell and put 8 electrons on it.
- Draw the third shell and put 18 electrons on it.
- Draw the fourth shell and put 18 electrons on it.
- Draw the fifth shell and put 4 electrons on it.
- Check: 2 + 8 + 18 + 18 + 4 = 50 electrons, the same as the number of protons.
From potassium onwards the shells don’t simply fill as 2, 8, 8: the fourth shell starts before the third is full, so the real arrangement above (2, 8, 18, 18, 4) is the one to draw.
Electron configuration
The electron configuration of tin is [Kr] 5s² 4d¹⁰ 5p². Its 4 outer electrons decide how it reacts: it tends to lose them, forming Sn²⁺ ions.
Key facts about tin
| Symbol | Sn |
|---|---|
| Atomic number | 50 |
| Relative atomic mass | 118.71 |
| Group · period · block | group 14 · period 5 · p-block |
| Type | Métal post-transitionnel |
| State at 25 °C | solid |
| Couches électroniques | 2, 8, 18, 18, 4 |
| Electron configuration | [Kr] 5s² 4d¹⁰ 5p² |
| Électrons de valence | 4 |
| Common ion | Sn²⁺ |
| Electronegativity (Pauling) | 1.96 |
| First ionisation energy | 7.34 eV (708 kJ/mol) |
| Atomic radius (empirical) | 145 pm |
Où tin sits on the periodic table
Foire aux questions
How many protons, neutrons and electrons does tin have?
Tin has 50 protons and 50 electrons (atomic number 50). Its most common isotope, tin-120, has 120 − 50 = 70 neutrons.
What is the electron configuration of tin?
[Kr] 5s² 4d¹⁰ 5p². In shells that is 2, 8, 18, 18, 4.
How many valence electrons does tin have?
4. Tin is in group 14, and its outer shell holds 4 electrons.
Where is tin on the periodic table?
In group 14, period 5, in the p-block. It is a post-transition metal.
