The oxidation state of an atom in a compound helps in determining the loss, gain or acquiring of electrons in a compound. The oxidation state of any element hence helps in determining the loss of electrons in a chemical compound during a chemical reaction. The highest oxidation state of any element is determined by the loss of all electrons during reactions for its stability. The lowest oxidation state elements are those which lose the least number of electrons to make them stable in a chemical reaction. The oxidation state of an atom is either positive, negative or zero. There are different rules which help in calculating the oxidation state of an element in the compound. The oxidation state of an element depends on the oxidation number of the other elements in the bond.

Elements with the highest oxidation state

Oxidation in a generation is the calculation of the degree of oxidation for an atom in a compound. There are some elements in the periodic table that have the highest oxidation state. Any element has the highest oxidation state when all of its valence electrons are taken by the atoms which form a covalent bond. The tetroxides elements like ruthenium, osmium, xenon, hassium etc. have the highest oxidation state. 

• The maximum oxidation state of osmium is +8. Even for the other elements belonging to the tetroxides, the maximum oxidation state is +8.
• Tetroxoiridium (IX) is the compound with iridium at highest oxidation state of +9.
• However, it is reported that there is a likelihood of obtaining an oxidation state of +12 for uranium when it is presented in the form of UO6. 
• The value of the highest oxidation state is always positive. 
• The more the positive value of the oxidation state, it means the elements have had more electrons removed for forming a stable form. Losing electrons is indicated by the positive value of the oxidation state. 

Elements with the lowest oxidation state 

• The atoms of elements in a compound that has the lowest oxidation state are those which stabilise themselves by losing the least number of electrons.
• Carbon has a different oxidation state depending on the compound it is bonded with. However, the carbon which in the CH4 (methane) has the lowest oxidation state. It has an oxidation state of -4.
• The lowest oxidation state of any element is for boron in the compound Al3BC with an oxidation state of -5. 
• The low oxidation state is always negative. 
• The more the negative value of the oxidation state, it means the elements have had more electrons removed for forming a stable form. Gaining electrons is indicated by the negative value of the oxidation state. 

General rules of the oxidation state of an element

The oxidation state of an element, highest or lowest, is determined and calculated by a set of rules. When there is an increase in the oxidation state of an element in a chemical reaction, it is termed oxidation. However, a decrease in the oxidation state of an atom is known as reduction. Hence, the elements that gain electrons have the lowest oxidation state. The elements which lose electrons are known to have the highest oxidation state.

• The sum of the oxidation state of the free or combined element in a compound is always zero. The atoms in their elementary state also have an oxidation state of zero.
• Hydrogen’s usual oxidation number is +1 but it varies in cases when it is bonded to metals that contain two elements.
• When halogens like halide and fluoride are present as halide ions, it has an oxidation number of -1. However, when halogens like bromine, iodine, and chlorine are combined with oxygen, it has a positive oxidation number.  

Oxidation states of Osmium and its stabilisation 

The maximum oxidation state of osmium is +8 during which all the valence electrons lose their electron forming an octet. The osmium has an oxidation state starting from – 2 to +8. The highest oxidation state of osmium with a value of +8 is present in osmium tetroxide. It is a toxic component produced when the powdered osmium is mixed and exposed to air. It has a high oxidation state because for the formation of osmium tetroxide, osmium requires losing all the valence electrons. The highest oxidation state of +8 means it forms an octet by sharing or losing all the eight electrons in the valence shells to another atom. Hence, low is the oxidation rate, it means a lower is the number of electrons osmium loses to form a stable form. The higher the oxidation state, means osmium loses a high number of electrons to form a stable bond. 

Conclusion 

The loss of an electron by an element in a compound is known as oxidation. Many elements lose electrons from their valence shell to form a bond between the adjoining atoms and stabilise the compounds. The value of the highest oxidation state is always positive and defines the maximum number of electrons lost by an element to make it stable. The lowest oxidation state has a negative value and indicates the electrons gained by an element to make it stable. Understanding the concept of oxidation state and rules applied for calculation is crucial for nomenclature. Hence, depending on the loss or gain of the electrons, the oxidation state can be negative, positive or even zero.