So oxidation number of Cr in K2Cr2O7 is +6.

Potassium trioxochlorochromate, Potassium chlorochromate, Peligot’s salt, or Péligot’s salt is a chemical substance named after Eugène-Melchior Péligot. Its formula is KCrO3Cl.

potassium chromate

Potassium chromate is the inorganic compound with the formula (K2CrO4). This yellow solid is the potassium salt of the chromate anion.

The oxygen atoms attached to Sulphur atom in the middle of the molecule are on the -O-O- Bond linkage and so these TWO oxygen atoms will possessthe Oxidation State of (-1), and all the other SIX oxygen atoms will possess the normal Oxidation State of (-2).

chlorite

+4

+1

Oxidation occurs when an atom, molecule, or ion loses one or more electrons in a chemical reaction. When oxidation occurs, the oxidation state of the chemical species increases. Oxidation doesn’t necessarily involve oxygen! Originally, the term was used when oxygen caused electron loss in a reaction.

+5

Hence the oxidation number of the Cl in Ca(ClO2)2is 3.

In hydrogen peroxide ,the oxidation number of hydrogen is +1 but its oxidation number is −1 when hydrogen is combined with less electronegative elements.

zero

-1

If an atom gains electron, the oxidation number is negative; if it looses electrons then the oxidation number is positive and if its octet is complete, oxidation number is zero.

Because we have neutral molecules the sum of all oxidation numbers must equal zero. In general the oxidation number of O is 2-, and those of F and Cl are 1-.

3.23 Chlorine can exist in both positive and negative oxidation states.

So Iodine (I) can exist in both positive and negative oxidation states.

Polonium hardly shows –2 oxidation states. Since electronegativity of oxygen is very high, it shows only a negative oxidation state as –2 except in the case of OF2 where its oxidation state is + 2.

-The oxidation state of fluorine is -1 always. -Then fluorine won’t show a positive oxidation number.

Yes non metals can have both positive and negative oxidation numbers.

Because the charge field density of the copper atom’s electron cloud moves a 4s into 3d. In zinc it’ll add a second electron to 4s. Welcome to chemistry. Thus, copper certainly does have 2 valence electrons it can lose, giving it an oxidized state of 2+.

The +1 ion has tetrahedral or square planar geometry. In solid compounds, copper(I) is often the more stable state at moderate temperatures. The copper(II) ion is usually the more stable state in aqueous solutions. Compounds of this ion, often called cupric compounds, are usually coloured.