Multiple Choice
Which of the following represents the correct orbital diagram for platinum (Pt, atomic number 78)?
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10. Periodic Properties of the Elements
The Electron Configuration
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Given the electron configuration of iron (Fe): [Ar] 4s2 3d6, how many core electrons and valence electrons does an iron atom have?
A
Core electrons: 10, Valence electrons: 16
B
Core electrons: 18, Valence electrons: 8
C
Core electrons: 20, Valence electrons: 6
D
Core electrons: 16, Valence electrons: 10
Verified step by step guidance1
Identify the electron configuration of iron (Fe), which is given as $[\text{Ar}]\ 4s^2\ 3d^6$. The notation $[\text{Ar}]$ represents the electron configuration of argon, the noble gas preceding iron.
Determine the number of electrons represented by the core configuration $[\text{Ar}]$. Argon has 18 electrons, so these 18 electrons are considered core electrons for iron.
Identify the valence electrons as those electrons outside the core configuration. For iron, these are the electrons in the $4s^2$ and $3d^6$ orbitals.
Count the valence electrons by adding the electrons in the $4s$ and $3d$ orbitals: $2$ electrons in $4s$ plus $6$ electrons in $3d$ gives a total of $8$ valence electrons.
Summarize the result: iron has $18$ core electrons (from $[\text{Ar}]$) and $8$ valence electrons (from $4s^2 3d^6$).
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