Identify the type of reaction in the following equation.
X + Y—— XY2

Can someone me with these questions plz.

Indicate whether the specified alkyl halides will form primarily substitution products, only elimination products, both substitution and elimination products, or no products when they react with sodium methoxide. 1-bromobutane 1-bromo-2-methylpropane 2-bromobutane 2-bromo-2-methylpropane

Will mark brainliest how many electrons can be held in the energy level n = 4?