Identify the correct Lewis electron-dot symbol for the following atoms.
As
O -As
: As:
. O As:
Se
O :Se
Se :
Se:
O :Se:
Ga
Ga :
Ga-
Ca.
Ca.
The Correct Answer and Explanation is :
The Lewis electron-dot symbol represents an atom’s valence electrons as dots around its chemical symbol. These symbols are essential for understanding chemical bonding and reactivity. Let’s analyze the given atoms and ions:
1. Arsenic (As):
Arsenic is in group 15 of the periodic table, indicating it has five valence electrons. The correct Lewis symbol is:
: As :This configuration places one dot on each side of the symbol, representing the five valence electrons.
2. Oxide Ion (O²⁻):
Oxygen, in group 16, has six valence electrons. The oxide ion (O²⁻) gains two electrons, resulting in eight valence electrons. The correct Lewis symbol is:
: O :²⁻This symbol shows eight dots around the oxygen symbol, indicating a full valence shell.
3. Selenium (Se):
Selenium, also in group 16, has six valence electrons. The correct Lewis symbol is:
: Se :This configuration places six dots around the selenium symbol, representing its valence electrons.
4. Gallium (Ga):
Gallium, in group 13, has three valence electrons. The correct Lewis symbol is:
: Ga :This symbol places three dots around the gallium symbol, indicating its valence electrons.
5. Calcium (Ca):
Calcium, in group 2, has two valence electrons. The correct Lewis symbol is:
: Ca :This configuration places two dots around the calcium symbol, representing its valence electrons.
Explanation:
The number of valence electrons corresponds to the group number for main-group elements. The Lewis symbol places dots around the element’s symbol to represent these electrons. For example, oxygen has six valence electrons, so its Lewis symbol has six dots. Similarly, calcium has two valence electrons, represented by two dots. These symbols are crucial for predicting how atoms will bond and interact in chemical reactions.