Asingle atom of an element has 21 neutrons, 20 electrons, and 20 protons. which element is it? k zr ca sc

Calcium

Explanation: As the element contains 20 electrons and 20 protons, it contains equal number of positive and negative charges, and thus it is a neutral atom.

Atomic number of an element = number of protons = number of electrons = 20

Thus the element is Ca with atomic number 20.

Mass number of an element = number of electrons + number of neutrons= 20+21= 41

Thus the representation of the element is:

Where X = chemical symbol

A = mass number

Z = atomic number

Thus the representation is

what is the average time it took the car to travel 0.25 meters?

⇒ 2.23 seconds

what is the average time it took the car to travel 0.50 meters?

⇒ 3.13 seconds

1 is the answer to this problem