Is "may be corrosive" a base, salt or acid

What is a possible quantum number set for an electron in the 3s orbital of a magnesium atom

Write the chemical formula for a compound that is made of an element from group 1 and an element from group 17

When the chemicals iron sulfide (fes) and hydrochloric acid (hcl) are combined, bubbles appear from the mixture. 1. does the appearance of bubbles indicate a physical or chemical change? 2. why do the bubbles indicate this change? 3. what property is this?