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secondary 4 | Chemistry
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Why is the answer B?
Date Posted: 3 years ago
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A proper answer can get very fundamental and requires an in depth study of electronegativity and molecular orbital combinations, but here is a simplified explanation :
Overall oxidation state of the compound K2O is 0 (neutral also means it is uncharged). K prefers to lose 1 electron to achieve the stable noble gas configuration (or octet configuration). Each K has an oxidation state of +1 since 1 electron is lost to O to form an ionic bond (K is less electronegative than O by the way)
Total oxidation state of the 2 K+ ions = +2
Since total oxidation state is 0, oxidation state of the O must be -2 in order to achieve this.
Subsequent explanation in comments.
Overall oxidation state of the compound K2O is 0 (neutral also means it is uncharged). K prefers to lose 1 electron to achieve the stable noble gas configuration (or octet configuration). Each K has an oxidation state of +1 since 1 electron is lost to O to form an ionic bond (K is less electronegative than O by the way)
Total oxidation state of the 2 K+ ions = +2
Since total oxidation state is 0, oxidation state of the O must be -2 in order to achieve this.
Subsequent explanation in comments.
Since O atom takes 2 electrons in total, it becomes a O²- ion (oxide ion)
Having 2 more electrons than its neutral configuration means the oxidation number is -2 (it got reduced)
Recall that oxidation can be thought of as the loss of electrons, reduction is the opposite.
Likewise,
Overall oxidation state of the compound K2O2 is 0 (neutral also means it is uncharged).
K prefers to lose 1 electron to achieve the stable noble gas configuration (or octet configuration).
Each K has an oxidation state of +1 since 1 electron is lost to O to form an ionic bond (K is less electronegative than O by the way)
Total oxidation state of the 2 K+ ions = +2
Since total oxidation state is 0, oxidation state of the two O must be -2 in order to achieve this.
Two O atoms are chemically equivalent and indistinguishable, their electronegativities are the same.
So each O takes in 1 electron equally and becomes singly negatively charged (O-) This also means the oxidation state of each O decreases by 1 (from 0 to -1)
But they are covalently bonded to each other as well (single bond), so it is a molecular ion.
⁻ :O-O: ⁻
The formula is O₂²⁻ (hence the term peroxide since the negative charge is distributed evenly per O atom)
Having 2 more electrons than its neutral configuration means the oxidation number is -2 (it got reduced)
Recall that oxidation can be thought of as the loss of electrons, reduction is the opposite.
Likewise,
Overall oxidation state of the compound K2O2 is 0 (neutral also means it is uncharged).
K prefers to lose 1 electron to achieve the stable noble gas configuration (or octet configuration).
Each K has an oxidation state of +1 since 1 electron is lost to O to form an ionic bond (K is less electronegative than O by the way)
Total oxidation state of the 2 K+ ions = +2
Since total oxidation state is 0, oxidation state of the two O must be -2 in order to achieve this.
Two O atoms are chemically equivalent and indistinguishable, their electronegativities are the same.
So each O takes in 1 electron equally and becomes singly negatively charged (O-) This also means the oxidation state of each O decreases by 1 (from 0 to -1)
But they are covalently bonded to each other as well (single bond), so it is a molecular ion.
⁻ :O-O: ⁻
The formula is O₂²⁻ (hence the term peroxide since the negative charge is distributed evenly per O atom)
Lastly for KO₂ (potassium superoxide),
The potassium ion is singly positively charged (K+) and since it lost 1 electron, the oxidation state is +1.
To balance this and have an overall oxidation state of 0, the oxidation state/number of the O₂ must be -1.
i.e these two Os take in 1 electron overall.
Since both O are chemically equivalent and indistinguishable, and the electronegativities are the same, the electron/negative charge is distributed evenly.
You can think of it as each O getting a -½ charge.
Hence O₂-
Since each gets ½ an electron's charge, the oxidation state is only reduced by ½ (from 0 to -0.5)
The potassium ion is singly positively charged (K+) and since it lost 1 electron, the oxidation state is +1.
To balance this and have an overall oxidation state of 0, the oxidation state/number of the O₂ must be -1.
i.e these two Os take in 1 electron overall.
Since both O are chemically equivalent and indistinguishable, and the electronegativities are the same, the electron/negative charge is distributed evenly.
You can think of it as each O getting a -½ charge.
Hence O₂-
Since each gets ½ an electron's charge, the oxidation state is only reduced by ½ (from 0 to -0.5)
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