# ABC graphs/Rules

### AB graph

A: Arrange atom symbols (Atoms)

B: Connect symbols with lines (Bonding paths)

### ABC graph

A: Arrange atom symbols (Atoms)

B: Connect symbols with lines (σ-Bonds)

C:

1. Find the most electronegative atoms evaluate its residual charge.
2. Calculate the residual charges for the rest of atoms accounting for the total charge value.

### ABCD graph

Rules
A. Arrange Atoms.
B. Allocate Bonds.
C. Assign Charges.
Hints
A. Hydrogen as well as more electronegative atoms tend to be terminal or (less commonly) bridging.
B. Few-member cycles are less favorable than linear arrangements.
C. Residual charge of terminal H/F/Cl/Br/I is 0 (not written), O/S is −, N is =, C is ≡.
Residual charge of bridging H/F/Cl/Br/I is +, O/S is 0 (not written), N is −.
Residual charge of the central atom is found using eq ΣC = q (total charge).
D. Number of dots equals D = A − B − C, where A is the number of the atoms' bonding electrons and B is the number of bonds around that atom.
A equals to the last digit of the group numbers.
Style
A. Use atom symbols.
B. Draw bonds with lines.
C. Write non-zero charges with characters: −, =, ≡, +, ⧺, ᚒ.
D. Draw dots as pairs or singles.

### ABD graph

A and B steps the same as for ABC graph.

D: For each atom of interest, find the number of bonding electrons (A), evaluate the oxidation number (O), but do not write it, then calculate D as D = A − O. Draw D dots around the atom in pairs of singles (Hund rule applies).

### ABDE and ABCDE graph

A–D steps the same as for ABD or ABCD graphs.

E: For each sp-atom of interest, calculate E as E = 4 − B − D· − D: Draw E hyper-ellipses around the atom.

### Control

Ensure that ΣC = q.

For geometrically similar arrangements prefer one with minimal sum of absolute residual charges Σ|C|. For example, O–O–C vs O–C–O and N–N–O vs N–O–N.

D can not be negative.