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For example, the complex [Ni(dien) 2)] 2+ is more stable than the complex [Ni(en) 3)] 2+; both complexes are octahedral with six nitrogen atoms around the nickel ion, but dien (diethylenetriamine, 1,4,7-triazaheptane) is a tridentate ligand and en is bidentate. The number of chelate rings is one less than the number of donor atoms in the ligand.
Because the leaving group bears a larger negative charge in the transition state (and products) than in the starting material, a good leaving group must be able to stabilize this negative charge, i.e. form stable anions. A good measure of anion stability is the pK a of an anion's conjugate acid (pK aH), and leaving group ability indeed ...
Atoms that lose electrons make positively charged ions (called cations). This transfer of electrons is known as electrovalence in contrast to covalence. In the simplest case, the cation is a metal atom and the anion is a nonmetal atom, but these ions can be more complex, e.g. polyatomic ions like NH + 4 or SO 2− 4.
A cation is a positively charged ion with fewer electrons than protons [2] (e.g. K + (potassium ion)) while an anion is a negatively charged ion with more electrons than protons. [ 3 ] (e.g. Cl − (chloride ion) and OH − (hydroxide ion)).
the extent of conjugation of the anion. Resonance effects can stabilize the anion. This is especially true when the anion is stabilized as a result of aromaticity. Geometry also affects the orbital hybridization of the charge-bearing carbanion. The greater the s-character of the charge-bearing atom, the more stable the anion.
This occurs during hydration of metal ions, so colorless anhydrous salts with an anion absorbing in the infrared can become colorful in solution. [81] Salts exist in many different colors, which arise either from their constituent anions, cations or solvates. For example: sodium chromate Na 2 CrO 4 is made yellow by the chromate ion CrO 2− 4.
As a result of its small size and high negative charge density, the fluoride anion is the "hardest" base (i.e., of low polarizability). Because of this, fluorides in real salt crystals often have higher effective charges than oxides of the same metal, even though oxygen's formal charge is twice as great as fluorine's. [citation needed]
A cation can be a conjugate acid, and an anion can be a conjugate base, depending on which substance is involved and which acid–base theory is used. The simplest anion which can be a conjugate base is the free electron in a solution whose conjugate acid is the atomic hydrogen.