If an atom of sodium combines with (captures) an alpha particle that has 2 protons and 2 neutrons, its new mass number will be
A)
13 amu
B)
15 amu
C)
25 amu
D)
27 amu

Question

If an atom of sodium combines with (captures) an alpha particle that has 2 protons and 2 neutrons, its new mass number will be
A)
13 amu	
B)
15 amu	
C)
25 amu	
D)
27 amu

australopithecus · Answer

Lets say that Sodium has a mass of 23 amu (based on molecular mass from periodic table)
A single Proton has a mass of 1 amu
A single Neutron has a mass of 1 amu

Thus you need to add up the total mass in amu of protons, neutrons and sodium atom to get your answer.


An interesting aside (not related too your question because your question deems it negligible ) but the total mass of the sum of the individual particles will be less than the mass of the combined particles due to nuclear binding energy and the famous equation E = MC^2