Answer:
The answer to your question is: 20
Explanation:
Atomic number is the number of proton and atom has. Each element has a specific number of protons, if the number of protons change, then this is a new element.
Mass number is the number of protons and neutrons and atom has.
Mass number = protons + neutrons
Data
Number of protons = ?
Atomic number = 20
Then,
atomic number = number of protons = 20
Answer:
180 m
Explanation:
The rock follows a free-fall motion - so the vertical distance covered can be found by using the equation

where
g = 10 m/s^2 is the acceleration due to gravity
t = 6.00 s is the time of the fall
Substituting these data, we find the height of the cliff:

Under the influence of gravity, objects just move down to the earth.
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Answer:
-2
Explanation:
Since its a compound, it's charge is 0.
So, there are 2 Fe and 3 Oxygen,
let x = oxidation number of oxygen
2(+3) + 3x =0
x =-2
Side note : even if the oxidation number is positive, make sure to put the positive sign like how you would in numbers