其實oxidation state係指..........

簡單 d 黎講, 即係該原子 ge 電子排佈 ge 各種可能情況
因為各種元素結合時都會有電子轉移或分享
但唔係點樣結合都得 ga ma
好似只有 H2O, H3O+, H2O2 唔會有 H5O 咁
而 oxidation state 就代表了它們的結合情況
作用就係如果唔知個樣野係乜
利用 oxidation state 就可以估到佢係乜

其他可能對你有用 ge 資料:

In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are represented by Arabic numerals and can be positive, negative, or zero. Thus, H+ would have an oxidation state of 1+.

The increase in oxidation state of an atom is known as an oxidation: a decrease in oxidation state is known as a reduction. Such reactions involve the transfer of electrons, a net gain in electrons being a reduction and a net loss of electrons being an oxidation.

Formal vs. spectroscopic oxidation states:

Although formal oxidation states can be helpful for classifying compounds, they are unmeasureable and their physical meaning can be ambiguous. Formal oxidation states require particular caution for molecules where the bonding is covalent, since the formal oxidation states require the heterolytic removal of ligands, which essentially denies covalency. Spectroscopic oxidation states, as defined by Jorgenson and reiterated by Wieghart, are measureables that are bench-marked using spectroscopic and crystallographic data.[1] Like many concepts in chemistry, spectroscopic oxidation states is powerful but requires collateral measurements. Formal oxidation states, on the other hand, result from arithmetic rules, not bonding. Skill in assigning formal oxidation states is considered essential, especially in inorganic chemistry.

Calculation of formal oxidation states:

There are two common ways of computing the oxidation state of an atom in a compound. The first one is used for molecules when one has a Lewis structure, as is often the case for organic molecules, while the second one is used for simple compounds (molecular or not) and does not require a Lewis structure.

It should be remembered that the oxidation state of an atom does not represent the "real" charge on that atom: this is particularly true of high oxidation states, where the ionization energy required to produce a multiply positive ion are far greater than the energies available in chemical reactions. The assignment of electrons between atoms in calculating an oxidation state is purely a formalism, albeit a useful one for the understanding of many chemical reactions.

The oxidation state is calculated by assuming there is charge in a compound.
If the compound is ionic, it's simply it's charge.
It the compound is polyatomic or covalent, thaen we first assume they have a charge.
For alkali metal, it's +1.
For alkaline earth metal, it's +2
For fluoride, it's -1.
FOr other element, it depends on the compound they form, whether they combine with element that are more eletronegative than them. Fluoride is the most eletronegative element, so it's oxidation state is always -1.
For others, like cluoride, it's usually -1, but it is not -1 in some cases, eg:when they form compound with fluoride, it becomes positive.
The higher eletronegativity, the more likely it has negative oxidation no.
The no. is determined by their charge when they are ions.
For the less eletronegative one, it's oxidation no. when add those of more eletronegative one must equal to the charge of the compound.

Oxidation is used for the ease to determine whether the reaction is redox or not, which part of compound is oxidized or reduced and predict which substance in a reaction is oxidizing agent or reducing agent.