Answer:
The period 4 alkaline-earth metal has the name Calcium. An isotope of this element having 20 neutrons has a mass number of 40.
Explanation:
Looking at the periodic table 4th row for the alkaline-earth metal, we can find Calcium which has an atomic number of 20 (or protons number, or z). The mass number is given by the sum of protons and neutrons. If the number of protons in this case is 20 and the number of neutrons is also 20, the mass number A = 40.
Answer:
The second option
Explanation:
Speed is defined at the rate at which distance changes with time. It is scalar quantity and it is expressed as shown below:
Speed = 
At constant speed the rate of change of distance with time is the same. On the second graph, this is noticeable. Both distance and time change at the same rate.
26, protons and nuetrons will always be the same
I think its B but im not sure...