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Counting
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Both counting methods give the same total, oxidation state and dⁿ; they differ in what each ligand gives. Answer choices are at least 2 apart on Easy and next to each other on Hard; changing the level deals another card. Geometry shows only the formula (no name, no structure, no cis/trans) until you answer: guess the shape from the number of ligands and the electron count. In the Ligands set, the other choices ask for the L/X class. Answer with All asks the electron count, oxidation state, dⁿ and geometry in turn. A card is mastered after two correct answers in a row, in every set that holds it; progress is saved in this browser. Ask All cards goes through every card once per pass, mastered ones too; Not mastered leaves out the cards you have mastered in Learn (in Name it, the complexes you named right last time). Star a card ☆, or drag it onto My cards, to keep it in your own set.

Periodic table, d block

The group number is the electron count of the neutral metal (covalent count); dⁿ = group − oxidation state.