Is the equation above balanced? How do you know? Mg + 2HCl → MgCl2 + H2

The above equation is balanced.

Explanation: Each individual atom are balanced. For Mg it has 1 atom in the reactant and product side. 2 atoms for H and 2 for Cl in both sides.

its first and third is your answer i did the qustion the fourth isnt right

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.