An atomic model shows 19 protons, 20 neutrons, and 19 electrons. What is the mass number of the atom? A. 39
B. 20
C. 58
D. 19

A. 39

Explanation:

Mass number= #protons + #neutrons

19+20= 39

for step 7 table c on the lab "newtons law of action"   the average time it took the car to travel .25 meters   was 1.92 seconds.

the average time it took the car to travel 0.50 meters was 2.61 seconds

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