Molecular structure

Question 1

Which is the main rule used to make Lewis structures?

Answer 1

The octet rule.

The main atom must have eight electrons in total, including its own and those it shares with the bonded atoms.

Question 2

What is the level of the periodic table where the octet rule applies?

Answer 2

The second level.

Higher levels involve d orbitals, so they expand their octet.

Question 3

Which is the Lewis structure for methane? And its molecular geometry?

Answer 3

(Photo with the Lewis structure)

CH4 has a tethaedral geometry, because it has no lone pairs of electrons and its general formula is AX4.

Question 4

What is the formula to know the formal charge of an atom?

Answer 4

Formal charge = V - N - B/2

Where:
V = number of valence electrons
N = non-bonding valence electrons
B= electrons shared in bonds

Question 5

What is the molecular geometry of PCl5?

Answer 5

Trigonal bipyramidal.

The main atom (P) has all of its valence electrones shared in bonds, with three Cl atoms in the same plane and the other two in axial positions.