The Lewis Dot Structure for arsenic trichloride, Ascl, will indicate which of the following:
a) A Total of 84 Electron Dots
b) Three Single Bonds and 10 Lone Pair Electrons
c) Two Single Bonds, One Double Bond, and 9 Lone Pair Electrons
d) One Single Bond, Two Double Bonds, and 8 Lone Pair Electrons
e) Three Single Bonds and Two Lone Pair Electrons
The correct answer and explanation is :
The correct answer is (e) Three Single Bonds and Two Lone Pair Electrons.
Explanation:
To determine the correct answer, we need to analyze the Lewis Dot Structure for arsenic trichloride (AsCl₃).
Step 1: Count the Total Valence Electrons
Arsenic (As) is in Group 15 of the periodic table, so it has 5 valence electrons. Chlorine (Cl) is in Group 17, so each chlorine atom has 7 valence electrons.
- Total valence electrons from arsenic: 5
- Total valence electrons from chlorine: 7 × 3 = 21
So, the total number of valence electrons in AsCl₃ is 5 + 21 = 26 electrons.
Step 2: Construct the Lewis Structure
In AsCl₃, arsenic is the central atom, and the chlorine atoms surround it. Arsenic will form single bonds with each chlorine atom, sharing one electron from arsenic with one electron from each chlorine.
- Each single bond between As and Cl uses 2 electrons.
- Three single bonds will thus use 6 electrons (2 electrons per bond × 3 bonds).
Step 3: Distribute the Remaining Electrons
After forming the three single bonds, we have used 6 electrons, leaving us with 26 – 6 = 20 electrons to distribute.
- Each chlorine atom will complete its octet by gaining 6 electrons (3 lone pairs) around it. This uses 18 electrons (6 electrons × 3 chlorine atoms).
- The remaining 2 electrons will be placed as a lone pair on the arsenic atom.
Step 4: Final Structure
- Arsenic has 3 single bonds with chlorine, and it has 1 lone pair of electrons.
- Each chlorine has 3 lone pairs of electrons and a single bond with arsenic.
Thus, the correct structure for arsenic trichloride (AsCl₃) has:
- Three single bonds between arsenic and chlorine atoms.
- Two lone pair electrons on the arsenic atom.
Therefore, the answer is (e) Three Single Bonds and Two Lone Pair Electrons.
Other Answer Choices:
- (a) is incorrect because there are only 26 electrons in total, not 84.
- (b) is incorrect because there are no double bonds and the lone pairs are not correctly assigned.
- (c) and (d) are also incorrect because they suggest double bonds, which do not occur in AsCl₃.