Which is the chemical name and formula for a compound containing the elements cesium and phosphorous?
A. cesium phosphorous, Cs3P
B. cesium phosphide, Cs3P
C. cesium triphosphide, CSP3
D. cesium phosphate, CSP3
The Correct Answer and Explanation is :
The correct answer is B. cesium phosphide, Cs₃P.
Explanation:
Cesium phosphide is an ionic compound formed from cesium (Cs), a Group 1 alkali metal, and phosphorus (P), a non-metal found in Group 15 of the periodic table. In ionic compounds, metals typically lose electrons to form positive ions (cations), while non-metals gain electrons to form negative ions (anions).
- Cation and Anion Formation:
- Cesium (Cs) has a valence electron configuration of ([Xe]6s^1), meaning it has one electron in its outermost shell. It readily loses this electron to form a cation, Cs⁺.
- Phosphorus (P), on the other hand, has a valence electron configuration of ([Ne]3s^23p^3), with five valence electrons. To achieve a stable octet, phosphorus typically gains three additional electrons, forming the phosphide anion, P³⁻.
- Stoichiometry:
- To balance the charge in the compound, three cesium ions (each with a +1 charge) are required to balance one phosphide ion (with a -3 charge). Therefore, the correct stoichiometry leads to the formula Cs₃P.
- Misleading Options:
- Option A (“cesium phosphorous, Cs₃P”) incorrectly names the compound, as it does not reflect the proper naming convention.
- Option C (“cesium triphosphide, CSP₃”) suggests a different ratio, which does not represent the correct charge balance.
- Option D (“cesium phosphate, CSP₃”) indicates a compound that would contain additional oxygen atoms (PO₄³⁻), characteristic of phosphate ions, which is not the case here.
Thus, cesium phosphide (Cs₃P) accurately represents the ionic compound formed between cesium and phosphorus, where the correct name and formula reflect the stoichiometry and the charges of the constituent ions.