What is the mass number of this element?

Write and balance the chemical equation that represents the reaction of aqueous sulfuric acid with aqueous sodium hydroxide to form water and sodium sulfate. include phases.

Stoichiometry- i need with 14 and 15! an explanation would be appreciated!

According to thomson, the atom is a positively charged cloud with electrons scattered throughout. what would the alpha particles do when they hit the foil if thomson were correct