Hey guys I need help with these questions on my test these are my questions I have not done it ***there are 4 pics I put***

Asample of radium-226 will decay 1/4 of its original amount after 3200years. what is the half-life of radium-226?

What is the mass of sodium in 3 moles of sodium chloride

Identify one disadvantage to each of the following models of electron configuration: -dot structures -arrow and line diagrams -written electron configurations type in your answer below. (answer) -dot structures do not show the distribution of electrons in orbitals and take up a lot of space. -arrow and line diagrams take up a lot of space and make it difficult to count electrons. -written configurations make it easy to lose count of electrons and do not show the distribution of electrons in orbitals.