Add electrons and charges as necessary to show the reaction of calcium and oxygen to form an ionic compound. Draw the Lewis structures of the neutral calcium and oxygen atoms. Incorrect ? Draw the Lewis structures of the calcium and oxide ions. Incorrect
The Correct Answer and Explanation is:
To correctly show the formation of an ionic compound between calcium (Ca) and oxygen (O), we need to:
- Draw the Lewis structures of the neutral atoms.
- Show the transfer of electrons.
- Draw the resulting ions with their charges and full outer electron shells.
1. Neutral Atoms – Lewis Structures:
- Calcium (Ca) has 2 valence electrons:
- Lewis structure: Ca:
- Oxygen (O) has 6 valence electrons:
- Lewis structure: ⋅⋅
:O:
⋅⋅
- Lewis structure: ⋅⋅
2. Electron Transfer:
- Calcium is a metal and loses 2 electrons to achieve a stable octet (like Argon).
- Oxygen is a nonmetal and gains 2 electrons to fill its octet (like Neon).
Thus:
- Calcium loses 2 electrons → becomes Ca²⁺
- Oxygen gains 2 electrons → becomes O²⁻
3. Ions – Lewis Structures:
- Calcium ion (Ca²⁺) has no valence electrons, full shell underneath.
- Lewis structure: [Ca]²⁺
- Oxide ion (O²⁻) has 8 valence electrons (6 original + 2 gained):
- Lewis structure:
[⋅⋅
:O:
⋅⋅]²⁻
- Lewis structure:
✅ Correct Ionic Compound Formation:
Ca + O → Ca²⁺ + O²⁻ → CaO
📝 Explanation
When calcium (Ca) and oxygen (O) react to form an ionic compound, the process involves the transfer of electrons from the metal to the nonmetal, forming oppositely charged ions held together by electrostatic attraction.
Calcium is an alkaline earth metal in Group 2 of the periodic table, with two electrons in its outermost shell. To attain a stable, noble gas configuration (like Argon), it tends to lose both of its valence electrons. When calcium loses two electrons, it becomes a calcium ion (Ca²⁺), with a full octet in the previous energy level and a +2 charge due to the loss of negative electrons.
Oxygen is a Group 16 element with six valence electrons. It needs two additional electrons to complete its octet and achieve a stable configuration (like Neon). Oxygen gains two electrons, forming an oxide ion (O²⁻) with a -2 charge. This ion has eight electrons in its valence shell.
The Lewis structure of neutral calcium is shown with two dots representing the two valence electrons, and for oxygen, six dots are drawn around the symbol. During the reaction, the two electrons from calcium are transferred to oxygen. In the final Lewis structures of the ions, calcium has no dots and is labeled with a 2+ charge, while oxygen has a full octet (eight dots) and a 2− charge.
The resulting ionic compound is CaO (calcium oxide), a stable substance where the electrostatic attraction between the Ca²⁺ and O²⁻ ions holds them together. This is a classic example of ionic bonding between a metal and a nonmetal, illustrating the principle of electron transfer leading to chemical stability.
