Understanding Lewis Structures and Charges

What is the first step in drawing a Lewis structure?

• Draw the molecular shape.

• Count the number of bonds needed.

• Determine the total number of valence electrons.

• Identify the central atom.

How do you determine the total number of valence electrons in a molecule?

• The total number of valence electrons in a molecule is the sum of the valence electrons of all its constituent atoms, adjusted for any ionic charges.

• Use the atomic number of each atom to find the total electrons.

• Multiply the number of atoms by 8 to get the total valence electrons.

• Count only the electrons in the outermost shell of the central atom.

What is the significance of lone pairs in a Lewis structure?

• Lone pairs have no impact on molecular stability.

• Lone pairs only affect the color of the molecule.

• Lone pairs are significant as they influence molecular geometry, reactivity, and stability.

• Lone pairs are irrelevant in determining molecular weight.

How do you calculate the formal charge of an atom in a molecule?

• Formal Charge = Non-bonding Electrons - Bonding Electrons

• Formal Charge = Valence Electrons + Bonding Electrons

• Formal Charge = Total Electrons - Non-bonding Electrons

• Formal Charge = Valence Electrons - (Non-bonding Electrons + 1/2 Bonding Electrons)

What is the formula for calculating formal charge?

• Formal Charge = 2 x Valence Electrons - (Non-bonding Electrons + Bonding Electrons)

• Formal Charge = Non-bonding Electrons + Bonding Electrons - Valence Electrons

• Formal Charge = Valence Electrons - (Non-bonding Electrons + 1/2 Bonding Electrons)

• Formal Charge = Valence Electrons + Non-bonding Electrons - 1/2 Bonding Electrons

What are resonance structures and why are they important?

• They are only relevant for ionic compounds.

• Resonance structures are alternative Lewis structures for a molecule that differ only in the placement of electrons. They are important for understanding the stability and reactivity of molecules.

• Resonance structures are the same as molecular shapes.

• Resonance structures represent different molecules entirely.

How do you identify resonance structures for a given molecule?

• Resonance structures can be identified by removing all lone pairs from the Lewis structure.

• Identify resonance structures by changing the arrangement of atoms in the molecule.

• Identify resonance structures by drawing valid Lewis structures that differ only in the placement of electrons, while keeping the arrangement of atoms the same.

• Draw only one Lewis structure without considering electron placement.

What is an example of a molecule that violates the octet rule?

• Carbon dioxide (CO2)

• Water (H2O)

• Ammonia (NH3)

• Phosphorus trifluoride (PF3)

What are the common exceptions to the octet rule?

• Molecules with exactly eight electrons

• Only molecules with even numbers of electrons

• All stable molecules must follow the octet rule

• Common exceptions to the octet rule include molecules with an odd number of electrons, expanded octets, and stable configurations with fewer than eight electrons.

How does molecular geometry relate to the arrangement of bonding and lone pairs?

• Molecular geometry is solely determined by the number of atoms in a molecule.

• Bonding pairs have no influence on the overall shape of a molecule.

• Lone pairs do not affect the bond angles in molecular geometry.

• Molecular geometry is influenced by the arrangement of bonding pairs and lone pairs, with lone pairs causing greater repulsion and altering bond angles.