3. Lewis Structure of NH₃

1. Count the total number of electrons (N_T) of the valence shell for all atoms of the molecule.

	Wrong. Check the number of electrons in N and H.
	Right/b>. N: 5; H: 1. Total 8 electrons
	Wrong. Check the number of electrons in N and H.

2. Select the central atom:

	Right. The less electronegative atom is usually the central atom. Hydrogen is excluded as central atom. N
	Wrong. The less electronegative atom is usually the central atom. Hydrogen is excluded as central atom.

3. How many electrons are used in the single bonds:

	Wrong. The three N-H bonds require more than three electrons.
	Wrong. The three N-H bonds require more than 4 electrons.
	Right. There are three N-H that require two electrons each one. Total 6 electrons

4. To complete the valence shell the terminal atoms need(electrons).

	Right.The hydrogen atom have their valence shell completed with the two electrons used in the N-H bonds . 0 electrons
	Wrong. The hydrogen atom have their valence shell completed with the two electrons used in the N-H bonds.

5. How many electrons needs the central atom to complete the valence shell?

	Wrong. The N atom shares 6 electrons with the H atoms. Needs two more electrons to complete the valence shell.
	Right. The N atom shares 6 electrons with the H atoms. Needs two more electrons to complete the valence shell. Locate them
	Wrong The N atom shares 6 electrons with the H atoms. Only needs two more electrons to complete the valence shell.

6. How is the geometry of the molecule? Structures

	Wrong. This molecule is of type AEX₃.
	Right. This molecule is of type AEX₃. The four electron pairs requiere a tetrahedral orientation. However, the three atoms take triangular pyramidal shape.
	Wrong This molecule is of type AEX₃. The four electron pairs requiere a tetrahedral orientation. The three atoms take three of the four position of the tetrahedral.

7. Are the bonds polar in this molecule? Electronegatividades

	Wrong. This molecule has polar bonds as N and H have different electronegativity.
	Right This molecule has polar bonds (N is more electronegative than H)

8. Is the molecule polar? Polarity

	Wrong. This molecule is polar as the bonds are polar and the dipolar moments are not canceled due to the pyramidal geometry.
	Right This molecule has polar bonds and the resulting dipolar moment is not zero.

9. What orbitals use the N atom.? Orbitals

	Wrong. Study the orbitals table.
	Wrong. Study the orbitals table.
	Right The N atom has four electron pairs around. Three are shared and one is unshared: AEX₃. That requires four orbitals: sp³orbitals.

3. Lewis Structure of NH3