The Correct Answer and Explanation is:
The correct answer is D.
To determine the correct Lewis dot structure for an element, we first need to find the number of valence electrons it possesses. Valence electrons are the electrons in the outermost energy shell of an atom, and they are the ones involved in chemical bonding.
Bismuth (Bi) is an element with the atomic number 83. By locating it on the periodic table, we can find its group and period. Bismuth is in Group 15 and Period 6. For main group elements, the group number (in the 1-18 system, the last digit) indicates the number of valence electrons. Therefore, as an element in Group 15, Bismuth has 5 valence electrons.
Alternatively, we can look at its electron configuration, which is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³. The outermost shell is the sixth shell (n=6), which contains 2 electrons in the 6s subshell and 3 electrons in the 6p subshell. Adding these together (2 + 3) gives us a total of 5 valence electrons.
The Lewis dot structure represents these valence electrons as dots around the element’s symbol. The standard convention for drawing these structures is to place one dot on each of the four sides (top, bottom, left, and right) before pairing them up.
For Bismuth’s 5 valence electrons:
- Place the first dot on top.
- Place the second dot on the right.
- Place the third dot on the bottom.
- Place the fourth dot on the left.
- Place the fifth dot next to one of the existing dots to form a pair.
This process results in a structure with one pair of electrons (a lone pair) and three single, unpaired electrons.
Let’s examine the given options:
- A and B show incorrect arrangements of the five electrons.
- C also shows an incorrect grouping of electrons, representing two lone pairs and one unpaired electron.
- D correctly shows one lone pair (the two dots at the bottom) and three unpaired electrons (one on the top, one on the left, and one on the right). This accurately reflects the 5 valence electrons of Bismuth.
