[Cr(OH₂){(O)₃}]⊖

Formula Unicode styled: 
[Cr(OH₂){(O)₃}]⊖
Compound name(s): 
aqua-trioxo-chromium(1-)
Central atom: 
Charge on formula unit (QN): 
1–
Compound type: 
Notes: 

The three oxo groups as a tetrahedral set are classified as X6L2 (neutral representation, 8 electrons, σ and π-bonding) for the d-block metal rather than X6 (three X2 groups). The three oxygen atoms possess 12 valence orbitals (18 electrons) and may be treated as sp hybridised. Three (occupied) point away from the metal and are non-bonding (6 electrons). One of the π-orbitals is represented as A2, has no corresponding combination on the metal (2 electrons), and so non-bonding. The remaining ten electrons constitute the X6L2 class. Overall there are nine bonding orbitals (3A1 and 3E) in point group (C3v) connecting the three oxo groups set and one L-type ligand with the metal. This is very similar to the situation for imino complexes [M(X)(NX)3]. See:

Valence Number (VN) = 𝘹 + 2𝘻 : 
Coordination Number (CN, sum of attached group denticities): 
Oxidation Number (ON) (Roman numerals): 
Electron Number (EN) = 𝘮 + 𝘹 +2𝘭: 
Bond number (BN) = 𝘹 + 𝘭 + 𝘻: 
9
[MLXZ]𝘲 class: 
[MX6L3]
MLXZ class (ENC, equivalent neutral class): 
MX6L3
Summary of calculated classifications: 
Cr«V6C4OVIE18B9Z0X6L3»
𝘥-electron configuration = 𝘮 – VN: 
d0
𝘥-electron configuration = 𝘮 – ON: 
d10
𝘥-electron configuration = 𝘮 – VN – 𝘲 from [MLXZ]𝘲: 
d0
Attached atoms: 
O4
Phase: 
InChIKey (see www.inchi-trust.org): 
QWPGUHVSOWSSAS-UHFFFAOYSA-N