How would you balance the following equation: $\mathrm{Mg}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to \mathrm{MgO}\left(\mathrm{s}\right)$

Balancing the Chemical equation:

• When we balance chemical equations, we want the same number of each sort of atom on both sides of the equation.
• Only the coefficients are changed. The numbers in front of the molecule are called coefficients.
• Subscripts should never be changed.
• Metals must be balanced first, followed by nonmetals such as oxygen and hydrogen.
• The unbalanced chemical reaction provided is

$\underset{\mathrm{Magnesium}}{\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}\mathrm{gas}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Magnesium}\mathrm{oxide}}{\mathrm{MgO}\left(\mathrm{s}\right)}$

• It is a combustion and redox process.

Reactant side	Product side
1 Magnesium atom from $\mathrm{Mg}$	1 Magnesium atom from $\mathrm{MgO}$
2 Oxygen atoms from ${\mathrm{O}}_2$	1 Oxygen atom from $\mathrm{MgO}$

• As we can see, there are two Oxygen atoms on the left, so we must put $2$ on the right side before Magnesium Oxide. $\underset{\mathrm{Magnesium}}{\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}\mathrm{gas}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Magnesium}\mathrm{oxide}}{2\mathrm{MgO}\left(\mathrm{s}\right)}$

Reactant side	Product side
1 Magnesium atom from $\mathrm{Mg}$	2 Magnesium atoms from $\mathrm{MgO}$
2 Oxygen atoms from ${\mathrm{O}}_2$	2 Oxygen atoms from $\mathrm{MgO}$

• Finally, Magnesium must be balanced, in this case, there is one $\mathrm{Mg}$ atom on the left and two $\mathrm{Mg}$ atoms on the product side, so we put a $2$ before Magnesium on the reactant side.; therefore, the equation is now balanced.

Reactant side	Product side
2 Magnesium atoms from $\mathrm{Mg}$	2 Magnesium atoms from $\mathrm{MgO}$
2 Oxygen atoms from ${\mathrm{O}}_2$	2 Oxygen atoms from $\mathrm{MgO}$

• Thus, the balanced chemical reaction is:

$\underset{\mathrm{Magnesium}}{2\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}\mathrm{gas}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Magnesium}\mathrm{oxide}}{2\mathrm{MgO}\left(\mathrm{s}\right)}$