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.


 * D. Add Dots.


 * 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.