Which of the following is the Lewis dot structure for one formula unit of calcium oxide
The Correct Answer and Explanation is:
The Lewis dot structure for one formula unit of calcium oxide (CaO) represents the bonding between a calcium atom (Ca) and an oxygen atom (O). Here’s how to determine the correct structure:
Step-by-Step Explanation:
- Electron Configuration:
- Calcium (Ca) is an alkaline earth metal in Group 2 of the periodic table. It has an atomic number of 20, meaning its electron configuration is:
Ca: 1s2 2s2 2p6 3s2 3p6 4s2\text{Ca:} \, 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 4s^2Ca:1s22s22p63s23p64s2
Calcium has two valence electrons in the 4s orbital (since it’s in Group 2), and it tends to lose these two electrons to achieve a stable electron configuration similar to that of a noble gas (in this case, argon). - Oxygen (O) is in Group 16 with an atomic number of 8, and its electron configuration is:
O: 1s2 2s2 2p4\text{O:} \, 1s^2 \, 2s^2 \, 2p^4O:1s22s22p4
Oxygen has six valence electrons, and it needs two more electrons to complete its octet, thus it tends to gain two electrons.
- Calcium (Ca) is an alkaline earth metal in Group 2 of the periodic table. It has an atomic number of 20, meaning its electron configuration is:
- Formation of Ions:
- Calcium (Ca) loses two electrons to form a Ca²⁺ ion. This leaves it with a stable electron configuration similar to argon.
- Oxygen (O) gains two electrons to form an O²⁻ ion, achieving a stable electron configuration like neon.
- Bonding:
- Calcium donates its two valence electrons to oxygen, forming an ionic bond between the Ca²⁺ and O²⁻ ions.
- Since this is an ionic bond, there are no shared electrons, but the bond is a result of the electrostatic attraction between the positively charged Ca²⁺ ion and the negatively charged O²⁻ ion.
Lewis Structure:
- Ca²⁺: This ion does not have any dots, as it has lost its valence electrons.
- O²⁻: This ion will have eight dots around it, representing its full octet.
Thus, the correct Lewis dot structure is represented as:
Ca²⁺ [O²⁻]
The two ions are attracted to each other in a 1:1 ratio to form calcium oxide, with the calcium ion and oxide ion held together by the ionic bond.
Conclusion:
In summary, the Lewis dot structure for one formula unit of calcium oxide (CaO) involves the calcium ion (Ca²⁺) with no dots (since it lost its electrons) and the oxide ion (O²⁻) with eight dots around it. This illustrates the ionic bonding between the two ions, making it a stable compound.
