Thallium (Tl): Bohr Model, Protons, Neutrons & Electrons
Thallium is element number 81, a post-transition metal in group 13, period 6. Its atom has 81 protons, 124 neutrons and 81 electrons arranged in 6 shells: 2, 8, 18, 32, 18, 3.
Protons, neutrons and electrons in thallium
ال atomic number of thallium is 81, so every thallium atom has 81 protons. A neutral atom has the same number of electrons, 81. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For thallium-205, that is 205 − 81 = 124 neutrons. Thallium has 2 stable isotopes, with 122, 124 neutrons.
How to draw the Bohr model of thallium
- Draw the nucleus and write 81 p⁺ تم تصميم [الخدمة] لمتعلمين من جميع الأعمار، بما في ذلك طلاب المدارس. 124 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 3 electrons on it.
- Check: 2 + 8 + 18 + 32 + 18 + 3 = 81 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, 3) is the one to draw.
Electron configuration
The electron configuration of thallium is [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p¹. Its 3 outer electrons decide how it reacts: it tends to lose them, forming Tl⁺ ions.
Key facts about thallium
| Symbol | Tl |
|---|---|
| Atomic number | 81 |
| Relative atomic mass | 204.38 |
| Group · period · block | group 13 · period 6 · p-block |
| نوع | Post-transition Metal |
| State at 25 °C | solid |
| أغلفة الإلكترون | 2, 8, 18, 32, 18, 3 |
| Electron configuration | [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p¹ |
| Valence electrons | 3 |
| Common ion | Tl⁺ |
| Electronegativity (Pauling) | 1.62 |
| First ionisation energy | 6.11 eV (590 kJ/mol) |
| Atomic radius (empirical) | 190 pm |
Where thallium sits on the periodic table
الأسئلة الشائعة
How many protons, neutrons and electrons does thallium have?
Thallium has 81 protons and 81 electrons (atomic number 81). Its most common isotope, thallium-205, has 205 − 81 = 124 neutrons.
What is the electron configuration of thallium?
[Xe] 6s² 4f¹⁴ 5d¹⁰ 6p¹. In shells that is 2, 8, 18, 32, 18, 3.
How many valence electrons does thallium have?
3. Thallium is in group 13, and its outer shell holds 3 electrons.
Where is thallium on the periodic table?
In group 13, period 6, in the p-block. It is a post-transition metal.
