Terbium (Tb): Bohr Model, Protons, Neutrons & Electrons
Terbium is element number 65, a lanthanide in the f-block (the lanthanide row drawn below the table), period 6. Its atom has 65 protons, 94 neutrons and 65 electrons arranged in 6 shells: 2, 8, 18, 27, 8, 2.
Protons, neutrons and electrons in terbium
ال atomic number of terbium is 65, so every terbium atom has 65 protons. A neutral atom has the same number of electrons, 65. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For terbium-159, that is 159 − 65 = 94 neutrons.
How to draw the Bohr model of terbium
- Draw the nucleus and write 65 p⁺ تم تصميم [الخدمة] لمتعلمين من جميع الأعمار، بما في ذلك طلاب المدارس. 94 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 27 electrons on it.
- Draw the fifth shell and put 8 electrons on it.
- Draw the sixth shell and put 2 electrons on it.
- Check: 2 + 8 + 18 + 27 + 8 + 2 = 65 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, 27, 8, 2) is the one to draw.
Electron configuration
The electron configuration of terbium is [Xe] 6s² 4f⁹. As a lanthanide it fills an inner f-subshell, and its common ion is Tb³⁺.
Key facts about terbium
| Symbol | Tb |
|---|---|
| Atomic number | 65 |
| Relative atomic mass | 158.93 |
| Group · period · block | f-block · period 6 |
| نوع | لانثانيد |
| State at 25 °C | solid |
| أغلفة الإلكترون | 2, 8, 18, 27, 8, 2 |
| Electron configuration | [Xe] 6s² 4f⁹ |
| Valence electrons | varies (outer shell: 2) |
| Common ion | Tb³⁺ |
| Electronegativity (Pauling) | 1.10 |
| First ionisation energy | 5.86 eV (565 kJ/mol) |
| Atomic radius (empirical) | 175 pm |
Where terbium sits on the periodic table
الأسئلة الشائعة
How many protons, neutrons and electrons does terbium have?
Terbium has 65 protons and 65 electrons (atomic number 65). Its most common isotope, terbium-159, has 159 − 65 = 94 neutrons.
What is the electron configuration of terbium?
[Xe] 6s² 4f⁹. In shells that is 2, 8, 18, 27, 8, 2.
How many valence electrons does terbium have?
Terbium is a lanthanide, so its valence electrons are spread over two shells; its outermost shell holds 2.
Where is terbium on the periodic table?
In the f-block (the lanthanide row drawn below the table), period 6, in the f-block. It is a lanthanide.
