Question

How many total electrons are transferred?

Li oxidation number is 0, Nitrogen is 0, in the compound Li is +1 and N is -6. Lithium lost 1 electron and Nitrogen gained 6 electrons. How is my answer wrong?

6 Li(s) + N2(g) → 2 Li3N(s)?

Answer 1

Answer:

For each unit of the reaction (i.e. for every two formula units of Li₃N produced,) six electrons will be transferred.

Explanation:

Lithium is a (new IUPAC) group 1 metal. In most compounds, it loses one atom to acquire an oxidation state of +1.

Nitrogen is a group 15 nonmetal. The oxidation state of N varies greatly from compounds to compounds. Let the oxidation state of N in the compound Li₃N be $x$.

Sum of the oxidation states on atoms in one unit of Li₃N:

$\underbrace{3 \times 1}_{\text{3 Li}\atop \text{atoms}} + \underbrace{1 \times (x)}_{\text{1 N}\atop \text{atom}} = x + 3$.

The oxidation state of all atoms in a neutral compound shall add up to 0. In other words,

$x + 3 = 0$.

Solve for $x$:

$x = -3$.

In other words, the oxidation state of N in the compound Li₃N is -3.

The oxidation state of both Li and N were initially 0.

• The oxidation state of Li increased from 0 to +1, meaning that each Li atom had lost one electron (to N.)
• The oxidation state of N decreased from 0 to -3, meaning that each N atom gained three electrons.

Note that each unit of nitrogen gas, N₂, contains two N atoms. Overall, the six Li atoms transferred $6 \times 1 = 6 = 2 \times 3$ electrons to the two N atoms.