Atomic No Of Calcium

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Its atomic number is 20. Its atomic mass is 40 u (approx). This discussion on What is the atomic no. And atomic mass of calcium? Is done on EduRev Study Group by Class 9 Students. 2020-11-21 by Nick Connor Atomic Mass of Calcium Atomic mass of Calcium is 40.078 u. Atomic number of calcium is 20. Number of protons = number of electrons = 20 First shell can accommodate 2 electrons so K = 2. Second shell can accommodate maximum of 8 electrons so L =8. The atomic number of calcium is 20. Electronic configuration of Calcium is Ar 4s2. It was discovered by Humphry Davy in 1808. Calcium is also found in ocean water and is about the eighth most abundant elementfound in the ocean.

What is the mass number of a Calcium atom if it has 20 neutrons?

1 Answer

Explanation:

First thing first, you need to make sure that you have a clear understanding of what mass number actually is.

As you know, the nucleus of an atom contains protons, which are positively charged particles, and neutrons, which are neutral particles.

An atom's mass number will always tell you how many protons and neutrons its nucleus contains.

#color(blue)('mass number' = 'no. of protons' + 'no. of neutrons')#

In your case, you know that an atom of calcium, #'Ca'#, has #20#neutrons in its nucleus.

This means that in order to get its mass number, all you need to know is how many protons are found in its nucleus.

As you know, the number of protons an atom contains in its nucleus is given by that atom's atomic number. A quick look in the periodic table will reveal that calcium has an atomic number equal to #20#.

Now, in order for an atom to be an atom of calcium, it Must contain #20# protons in its nucleus. Always. The number of neutrons can vary, but the number of protons must always be equal to #20# for a calcium isotope.

Therefore, the mass number of this calcium isotope will be

#'mass number' = A = '20 protons' + '20 neutrons' = 40#

You are dealing with the calcium-40 isotope, #'_20^40'Ca'#.

2 Answers

Explanation:

There are few simple rules to follow.

(1) The atomic number is equal to the number of protons.

#Z# = number of protons

(2) In neutrally charged elements, the number of electrons is the same as the number of protons.

#Z# = number of protons = number of electrons (no charge)

Otherwise, positive charge means that the element lost an electron and negative charge means it gained an electron.

(3) The atomic mass is equal to the sum of the number of protons and number of neutrons.

#A# = number of protons + number neutrons