What element has 10 protons and 12 electrons and 10 neutrons

Magnesium Ion

Explanation:

This is a Magnesium ion. There are 12 protons from the magnesium atom. There are 10 electrons because 12-2=10. There are 12 neutrons because 24-12=12

h

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.