The procedure in the question describes venopuncture.
Venopuncture is the method of aseptically collecting blood into the right sample containers. Using a stopper-punturing needle and a vacuum tube, the following procedure is followed:
assemble the needle and hub (needle holder)
apply the tourniquet and examine the arm for palpable vein, palpate the vein
release the tourniquet and swab the collection site with 70% alcohol
allow the swab to dry
reapply the tourniquet
insert the stopper-puncturing needle (attached to hub) into the appropriate vein
after the vein is entered, the stopper-puncturing needle should be completely pushed into the evacuated (vacuum) tubes
blood will flow into the tube until vacuum is completely filled
pull out the tube and invert gently several times if the tube contains anticoagulants
place a gauze on the site of puncture (do not press down the gauze)
remove the needle and press down the gauze immediately
dispose the needle into the sharps container or appropriately
Explanation:you find neutrons by subtracting the mass number from the proton for this example lithium's number of protons is 3 and mass number 9 so 9-3=6