Which element, indicated by letter on the periodic table above, contains one f electron?
A) A
B) B
C) C
D) D
The correct answer and explanation is :
It looks like you’re referring to a periodic table image with labeled elements by letters (A, B, C, D), but I don’t see the image attached here. To answer which element contains one f electron, I need to clarify a bit about the f block and the electronic configuration of elements.
Understanding the f-electrons and the periodic table:
- f-electrons are electrons in the f orbitals, which are characteristic of the lanthanide and actinide series.
- The f-block elements are located in periods 6 and 7, between groups 3 and 4.
- The first f electron appears at lanthanum (La) or cerium (Ce) in the lanthanide series, depending on interpretation.
- The electron configuration for the first lanthanide with one f electron is typically [Xe] 6s² 5d¹ 4f¹ or [Xe] 6s² 4f¹ 5d¹ depending on subtle variations, but practically cerium (Ce) is considered the first to start filling the 4f orbital.
Which element contains one f electron?
- The element with one f electron is the one starting the filling of the f orbitals in the lanthanide series: Cerium (Ce).
- Cerium’s electron configuration: [Xe] 6s2 4f1 5d1\mathrm{[Xe]\, 6s^2\, 4f^1\, 5d^1}
- Thus, Cerium contains exactly one electron in the 4f subshell.
If your letter choices correspond to:
- A = Lanthanum (La) — typically 4f^0 (no f electron in La)
- B = Cerium (Ce) — 4f^1 (one f electron)
- C = Praseodymium (Pr) — 4f^3 (more than one f electron)
- D = Neodymium (Nd) — 4f^4 (more than one f electron)
Then the correct answer would be B (Cerium).
Explanation in detail (300 words):
In the periodic table, elements are arranged by increasing atomic number and grouped according to their electron configurations. The f-block elements, which include the lanthanides and actinides, are characterized by filling their f orbitals. The filling of the f orbitals starts with the lanthanide series, which begins after lanthanum (La, atomic number 57).
Lanthanum itself has an electron configuration that does not include electrons in the 4f orbital, often written as [Xe] 5d1 6s2\mathrm{[Xe]\, 5d^1\, 6s^2}, meaning the f orbitals remain empty here. The very next element, cerium (Ce), starts the filling of the 4f orbital. Cerium has one electron in the 4f subshell, with the electron configuration [Xe] 6s2 4f1 5d1\mathrm{[Xe]\, 6s^2\, 4f^1\, 5d^1}. This marks the first appearance of f-electrons in the periodic table.
After cerium, other lanthanides fill the 4f orbitals with increasing numbers of electrons: praseodymium has three 4f electrons, neodymium has four, and so on, filling up to fourteen f electrons in total for the last lanthanide, lutetium.
Identifying which element contains exactly one f electron is essential in understanding the chemistry and electronic structure of the f-block elements. Cerium’s unique position makes it the first element with an f electron, impacting its chemical properties and behavior in comparison to lanthanum, which has none.
Summary:
The element with one f electron is the first lanthanide to start filling the 4f orbital — Cerium (Ce), corresponding to choice B in your question