السيريم (Ce): Bohr Model, Protons, Neutrons & Electrons
السيريم is element number 58, a lanthanide in the f-block (the lanthanide row drawn below the table), period 6. Its atom has 58 protons, 82 neutrons and 58 electrons arranged in 6 shells: 2, 8, 18, 19, 9, 2.
Protons, neutrons and electrons in cerium
ال atomic number of cerium is 58, so every cerium atom has 58 protons. A neutral atom has the same number of electrons, 58. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For cerium-140, that is 140 − 58 = 82 neutrons. Cerium has 4 stable isotopes, with 78, 80, 82, 84 neutrons.
How to draw the Bohr model of cerium
- Draw the nucleus and write 58 p⁺ تم تصميم [الخدمة] لمتعلمين من جميع الأعمار، بما في ذلك طلاب المدارس. 82 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 19 electrons on it.
- Draw the fifth shell and put 9 electrons on it.
- Draw the sixth shell and put 2 electrons on it.
- Check: 2 + 8 + 18 + 19 + 9 + 2 = 58 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, 19, 9, 2) is the one to draw.
Electron configuration
The electron configuration of cerium is [Xe] 6s² 4f¹ 5d¹. As a lanthanide it fills an inner f-subshell, and its common ion is Ce³⁺.
Key facts about cerium
| Symbol | Ce |
|---|---|
| Atomic number | 58 |
| Relative atomic mass | 140.12 |
| Group · period · block | f-block · period 6 |
| نوع | لانثانيد |
| State at 25 °C | solid |
| أغلفة الإلكترون | 2, 8, 18, 19, 9, 2 |
| Electron configuration | [Xe] 6s² 4f¹ 5d¹ |
| Valence electrons | varies (outer shell: 2) |
| Common ion | Ce³⁺ |
| Electronegativity (Pauling) | 1.12 |
| First ionisation energy | 5.54 eV (535 kJ/mol) |
| Atomic radius (empirical) | 185 pm |
Where cerium sits on the periodic table
الأسئلة الشائعة
How many protons, neutrons and electrons does cerium have?
Cerium has 58 protons and 58 electrons (atomic number 58). Its most common isotope, cerium-140, has 140 − 58 = 82 neutrons.
What is the electron configuration of cerium?
[Xe] 6s² 4f¹ 5d¹. In shells that is 2, 8, 18, 19, 9, 2.
How many valence electrons does cerium have?
Cerium is a lanthanide, so its valence electrons are spread over two shells; its outermost shell holds 2.
Where is cerium 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.
