# REDOX question

#### markosheehan

##### Member
can some one show me by looking at electrons lost and gained which is oxidised and reduced in the reaction

2ca+o2->2cao

i would of said each calcium atom has a O.N of +2 and o2 has a O.N of 0
the o in 2cao has a O.N of -2 so that means the ca has a O.N of +2. but that makes no sense. where did as where did the oxygen gain the 2 electrons if the O.N of ca stays the same

im doing these questions wrong

#### Klaas van Aarsen

##### MHB Seeker
Staff member
can some one show me by looking at electrons lost and gained which is oxidised and reduced in the reaction

2ca+o2->2cao

i would of said each calcium atom has a O.N of +2 and o2 has a O.N of 0
the o in 2cao has a O.N of -2 so that means the ca has a O.N of +2. but that makes no sense. where did as where did the oxygen gain the 2 electrons if the O.N of ca stays the same

im doing these questions wrong
Both $\ce{Ca}$ and $\ce{O2}$ are neutral.
In $\ce{CaO}$, $\ce{Ca}$ has oxidation number +2 and $\ce{O}$ has oxidation number -2.
$\ce{Ca}$ is oxidized and $\ce{O}$ is reduced.

#### MarkFL

Staff member
can some one show me by looking at electrons lost and gained which is oxidised and reduced in the reaction

2ca+o2->2cao
We have MathJax configured to handled chemical equations...for example the following code:

\ce{2Ca + O2 -> 2CaO}

produces:

$$\displaystyle \ce{2Ca + O2 -> 2CaO}$$

Both $\ce{Ca}$ and $\ce{O2}$ are neutral.
In $\ce{CaO}$, $\ce{Ca}$ has oxidation number +2 and $\ce{O}$ has oxidation number -2.
$\ce{Ca}$ is oxidized and $\ce{O}$ is reduced.