Answer:
The answer to your question is: Element
Explanation:
Question 1. The atomic number or proton number of an atom has the symbol Z. This number indicates the number of protons and element has. Each elelement has a specific atomic number, two different atomic numbers mean 2 different elements.
From the options given, we conclude that the element is different.
For atoms in the periodic table, the given mass number is the sum of the number of the protons (also called the atomic number) and the number of the neutrons inside its nucleus. Mathematically,
mass number = atomic number + number of neutrons
Substituting,
39 = 19 + n
n = 39 - 19 = 20
Therefore, the answer is not found in the choices.
Letra a obrigadoaijahahavqvqgqgqg
The speed of a electron that is accelerated from rest through an electric potential difference of 120 V is 
<h3>
How to calculate the speed of the electron?</h3>
We know, that the energy of the system is always conserved.
Using the Law of Conservation of energy,
U=0
Here, K is the kinetic energy and U is the potential energy.
Now, substituting the formula of U and K, we get:
=0------(1)
Here,
m is the mass of the electron
v is the speed of the electron
q is the charge on the electron
V is the potential difference
Let 
and 
represent the final and initial speed.
Here, =0
Solving for , we get:
=6.49
m/s
To learn more about the conservation of energy, refer to:
brainly.com/question/2137260
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