Multiple Choice
In the Lewis dot structure of the neutral compound CH2O (formaldehyde), how many lone pairs of electrons are present on the central atom?
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11. Bonding & Molecular Structure
Lewis Dot Structures: Neutral Compounds
Multiple Choice
Which of the following is the correct Lewis electron dot structure for neutral magnesium chloride (MgCl_2)?
A
Mg^{2+} [ :Cl: ] [ :Cl: ]
B
Mg [ :Cl: ] [ :Cl: ]
C
Mg^{2+} [ :Cl: ]^{-} [ :Cl: ]^{-}
D
Mg [ :Cl: ]^{-} [ :Cl: ]^{-}
Verified step by step guidance1
Step 1: Identify the nature of bonding in magnesium chloride (MgCl_2). Magnesium is a metal and chlorine is a nonmetal, so MgCl_2 is an ionic compound formed by the transfer of electrons from magnesium to chlorine atoms.
Step 2: Determine the electron configuration changes. Magnesium (Mg) starts with 2 valence electrons and tends to lose both to achieve a stable noble gas configuration, becoming Mg^{2+}. Each chlorine atom (Cl) needs one electron to complete its octet, so each Cl gains one electron, becoming Cl^{-}.
Step 3: Draw the Lewis structure for the ions. Represent Mg as Mg^{2+} with no dots around it because it has lost its valence electrons. Each Cl^{-} should be shown with 8 dots (4 pairs) around the symbol to represent the full octet, and a negative charge to indicate the extra electron.
Step 4: Combine the ions to form the neutral compound. Since Mg^{2+} has a +2 charge and each Cl^{-} has a -1 charge, two Cl^{-} ions balance the charge of one Mg^{2+} ion, resulting in a neutral MgCl_2 compound.
Step 5: Verify the overall charge and octet completion. Ensure that the Mg ion has no valence electrons (due to loss) and each Cl ion has a complete octet with a negative charge, confirming the correct Lewis electron dot structure is Mg^{2+} [ :Cl: ]^{-} [ :Cl: ]^{-}.
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