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Ch.8 - Basic Concepts of Chemical Bonding
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Capitolo 8, Problema 68b

Some chemists believe that satisfaction of the octet rule should be the top criterion for choosing the dominant Lewis structure of a molecule or ion. Other chemists believe that achieving the best formal charges should be the top criterion. Consider the dihydrogen phosphate ion, H2PO4-, in which the H atoms are bonded to O atoms. (b) What is the predicted dominant Lewis structure if achieving the best formal charges is the top criterion?

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Identify the total number of valence electrons in the dihydrogen phosphate ion (H2PO4-). Phosphorus (P) has 5 valence electrons, each oxygen (O) has 6, and each hydrogen (H) has 1. Additionally, add 1 electron for the negative charge.
Arrange the atoms with phosphorus as the central atom, and attach the oxygen atoms and hydrogen atoms to the oxygens. Remember that hydrogen can only form one bond.
Distribute the electrons to satisfy the octet rule for the central phosphorus and the oxygen atoms, while ensuring that each hydrogen atom is connected to an oxygen atom with a single bond.
Calculate the formal charges for each atom. The formal charge is calculated using the formula: Formal Charge = (Valence electrons) - (Non-bonding electrons) - 0.5*(Bonding electrons).
Choose the structure that minimizes the formal charges on each atom, aiming for a structure where the sum of the formal charges equals the overall charge of the ion, which is -1 in this case.

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Octet Rule

The octet rule is a chemical guideline stating that atoms tend to bond in such a way that they each have eight electrons in their valence shell, achieving a stable electron configuration similar to that of noble gases. This rule helps predict the arrangement of electrons in molecules and is crucial for understanding molecular stability and reactivity.
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Formal Charge

Formal charge is a theoretical charge assigned to an atom in a molecule, calculated by taking the number of valence electrons, subtracting the number of non-bonding electrons, and half the number of bonding electrons. It helps chemists determine the most stable Lewis structure by minimizing formal charges across the molecule, leading to a more favorable electron distribution.
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Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They are essential for visualizing molecular geometry and electron distribution, allowing chemists to predict the behavior of molecules in chemical reactions and their interactions with other substances.
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Percorso guidato
04:28
Lewis Dot Structures: Ions