University:
University of North Carolina at Charlotte
Course:
CHEM 1251 | General Chemistry I
Academic year:

2024
Views:

348

Pages:

10
Author:

Kamila P.

CHAPTER 6 REPRESENTING MOLECULES LEWIS STRUCTURE BASIC It shows which atoms in a molecule are bonded to each other, and how electrons are shared between the atoms. VALENCE Electrons are represented by dots and lines. A pair of nonbonding electrons (:) is a LONE PAIR. A shared pair of electrons is a BONDING PAIR. -1 line represents a SINGLE bond. -2 lines represent a DOUBLE bond. -3 lines represent a TRIPLE bond. 3. DISTRIBUTE THE ELECTRONS AMONG THE ATOMS, GIVING OCTETS (8 ELECTRONS) TO AS MANY ATOMS AS POSSIBLE. (Exception: H can only have a duet - 2 electrons) a) Start by placing two electrons between every 2 atoms, shown as a line (→ a single bond or 2e). b) Then distribute the remaining electrons as lone pairs. First add lone pairs to terminal (outer) atoms. Next, add lone pairs to the central atom. We will cover exceptions to the octet rule (more or less than 8 electrons). 4. IF ANY ATOMS DO NOT HAVE AN OCTET, FORM DOUBLE (=) OR TRIPLE (=) BONDS AS NECESSARY TO GIVE THEM OCTETS. Do this by moving lone electron pairs from terminal atoms into the bonding region with the central atom (between atoms). 5. CHECK YOUR LEWIS STRUCTURE: Does it have the correct number of electrons? WHEN LEWIS STRUCTURE GET MORE COMPLICATED... Draw the Lewis Structure for NO₂ STEP 1: SKELETAL STRUCTURE ONO STEP 2: TOTAL NUMBER OF ELECTRONS N: 5e O: 6e * 2 = 12e 23e + 1e = 24e STEP 3-5: DISTRIBUTE ELECTRONS BETWEEN ATOMS, THEN TO TERMINAL ATOMS, THEN CREATE DOUBLE OR TRIPLE BONDS TO FILL OCTETS. PUT BRACKETS AROUND THE STRUCTURE AND INCLUDE THE CHARGE. CHECK YOUR ANSWER. [O-N=O]⁻ [O=N-O]⁻ [O-N≡O]⁺ We have 3 possibilities. THIS IS CALLED RESONANCE BECAUSE WE HAVE DIFFERENT POSITIONS FOR THE DOUBLE BOND. (DIFFER ONLY IN THE POSITION OF THE ELECTRONS) In reality, the molecule exists as an average of the resonance forms (a resonance hybrid).