Thorium (Th): Bohr Model, Protons, Neutrons & Electrons
Thorium is element number 90, an actinide in the f-block (the actinide row drawn below the table), period 7. Its atom has 90 protons, 142 neutrons and 90 electrons arranged in 7 shells: 2, 8, 18, 32, 18, 10, 2.
Protons, neutrons and electrons in thorium
ال atomic number of thorium is 90, so every thorium atom has 90 protons. A neutral atom has the same number of electrons, 90. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For thorium-232, that is 232 − 90 = 142 neutrons. Every isotope of thorium is radioactive; 232 is the mass number of its most stable one.
How to draw the Bohr model of thorium
- Draw the nucleus and write 90 p⁺ تم تصميم [الخدمة] لمتعلمين من جميع الأعمار، بما في ذلك طلاب المدارس. 142 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 32 electrons on it.
- Draw the fifth shell and put 18 electrons on it.
- Draw the sixth shell and put 10 electrons on it.
- Draw the seventh shell and put 2 electrons on it.
- Check: 2 + 8 + 18 + 32 + 18 + 10 + 2 = 90 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, 32, 18, 10, 2) is the one to draw.
Electron configuration
The electron configuration of thorium is [Rn] 7s² 6d². As an actinide it fills an inner f-subshell, and its common ion is Th⁴⁺.
Key facts about thorium
| Symbol | Th |
|---|---|
| Atomic number | 90 |
| Relative atomic mass | 232.04 |
| Group · period · block | f-block · period 7 |
| نوع | الأكتينيد |
| State at 25 °C | solid |
| أغلفة الإلكترون | 2, 8, 18, 32, 18, 10, 2 |
| Electron configuration | [Rn] 7s² 6d² |
| Valence electrons | varies (outer shell: 2) |
| Common ion | Th⁴⁺ |
| Electronegativity (Pauling) | 1.30 |
| First ionisation energy | 6.31 eV (609 kJ/mol) |
| Atomic radius (empirical) | 180 pm |
Where thorium sits on the periodic table
الأسئلة الشائعة
How many protons, neutrons and electrons does thorium have?
Thorium has 90 protons and 90 electrons (atomic number 90). Its most common isotope, thorium-232, has 232 − 90 = 142 neutrons.
What is the electron configuration of thorium?
[Rn] 7s² 6d². In shells that is 2, 8, 18, 32, 18, 10, 2.
How many valence electrons does thorium have?
Thorium is an actinide, so its valence electrons are spread over two shells; its outermost shell holds 2.
Where is thorium on the periodic table?
In the f-block (the actinide row drawn below the table), period 7, in the f-block. It is an actinide.
