Formal Charges and Valence Electrons

The video tutorial explains how to calculate the formal charge for each element in hydrofluoric acid (HF) using the Lewis structure. It details the process for hydrogen and fluorine, showing that both have a formal charge of zero. The tutorial concludes that when formal charges are zero or close to zero, it indicates the most favorable Lewis structure. This is demonstrated as the best structure for HF.

What is the first step in calculating formal charges using the Lewis structure?

• Count the total number of electrons in the molecule.

• Identify the number of protons in the atom.

• Calculate the molecular weight of the compound.

• Determine the number of valence electrons for each atom.

How many valence electrons does hydrogen have in HF?

• Two

• One

• Three

• Four

What is the formal charge on hydrogen in HF after calculation?

• -1

• +1

• +2

• 0

In which group is fluorine found on the periodic table?

• Group 1

• Group 17

• Group 2

• Group 18

How many unbonded valence electrons does fluorine have in HF?

• Four

• Eight

• Two

• Six

What is the formal charge on fluorine in HF after calculation?

• +1

• -1

• 0

• +2

What does a formal charge of zero indicate about a Lewis structure?

• It is unstable.

• It is the most likely or favorable structure.

• It is incorrect.

• It has too many electrons.

What is the best Lewis structure for HF based on formal charges?

• One where both hydrogen and fluorine have a formal charge of zero.

• One with a negative charge on fluorine.

• One with a positive charge on hydrogen.

• One with a double bond between hydrogen and fluorine.