You discover that an atom of an unknown element has 54 protons, Identify the element and explain how you know the identity is correct
Explain whether the unknown element is more or less reactive than an atom of an element that has 30 protons,
Identify an element that would have very similar chemical properties to the unknown element and explain why its chemical properties would be similar

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.