Platinum (Pt): Bohr Model, Protons, Neutrons & Electrons
Platinum is element number 78, a transition metal in group 10, period 6. Its atom has 78 protons, 117 neutrons and 78 electrons arranged in 6 shells: 2, 8, 18, 32, 17, 1.
Protons, neutrons and electrons in platinum
The atomic number of platinum is 78, so every platinum atom has 78 protons. A neutral atom has the same number of electrons, 78. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For platinum-195, that is 195 − 78 = 117 neutrons. Platinum has 6 stable isotopes, with 112, 114, 116, 117, 118, 120 neutrons.
How to draw the Bohr model of platinum
- Draw the nucleus and write 78 p⁺ and 117 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 17 electrons on it.
- Draw the sixth shell and put 1 electron on it.
- Check: 2 + 8 + 18 + 32 + 17 + 1 = 78 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, 17, 1) is the one to draw.
Electron configuration
The electron configuration of platinum is [Xe] 6s¹ 4f¹⁴ 5d⁹. As a transition metal it fills an inner d-subshell, and its common ion is Pt²⁺.
Key facts about platinum
| Symbol | Pt |
|---|---|
| Atomic number | 78 |
| Relative atomic mass | 195.08 |
| Group · period · block | group 10 · period 6 · d-block |
| Type | Transition Metal |
| State at 25 °C | solid |
| Electron shells | 2, 8, 18, 32, 17, 1 |
| Electron configuration | [Xe] 6s¹ 4f¹⁴ 5d⁹ |
| Valence electrons | varies (outer shell: 1) |
| Common ion | Pt²⁺ |
| Electronegativity (Pauling) | 2.28 |
| First ionisation energy | 8.96 eV (865 kJ/mol) |
| Atomic radius (empirical) | 135 pm |
Where platinum sits on the periodic table
Frequently asked questions
How many protons, neutrons and electrons does platinum have?
Platinum has 78 protons and 78 electrons (atomic number 78). Its most common isotope, platinum-195, has 195 − 78 = 117 neutrons.
What is the electron configuration of platinum?
[Xe] 6s¹ 4f¹⁴ 5d⁹. In shells that is 2, 8, 18, 32, 17, 1.
How many valence electrons does platinum have?
Platinum is a transition metal, so its valence electrons are spread over two shells; its outermost shell holds 1.
Where is platinum on the periodic table?
In group 10, period 6, in the d-block. It is a transition metal.
