Calculate the mass number for an element which has the atomic number 12, knowing that the number of protons is the same with the number of neutrons. Also find out the electronical configuration and...

Calculate the mass number for an element which has the atomic number 12, knowing that the number of protons is the same with the number of neutrons.

Also find out the electronical configuration and the position of the element in periodic table.

 

Asked on by albimaia

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giorgiana1976's profile pic

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted on

We'll use the following notation:

A-mass number

Z-atomic number

The mass number could be calculated as a sum of protons and neutrons, and knowing that the atomic number is given by the number of the protons, that means that Z=12, so we'll have 12 protons.

In the enunciation is given the information that the number of protons and the number of neutrons are equal, so we'll have 12 neutrons, too.

A=protons+neutrons=12+12=24

The electronical configuration will be found out based on the fact that the number of protons is also equal to the number of electrons, so the element will have 12 electrons.

We'll fill up the  levels, according to the maximum number of electrons accepted on each level.

On the first level K, the element will have 2 electrons.

On the next level L, the element will have 8 electrons.

On the following level, M, the element will have the rest of 2 electrons.

The total number of electrons:2+8+2=12.

Searching for the element in the periodic table, knowing it's atomic number Z=12, it will be located on the 12th position, and this element is Magnesium.

krishna-agrawala's profile pic

krishna-agrawala | College Teacher | (Level 3) Valedictorian

Posted on

The mass number of a chemical element, usually represented by 'A, is defines as the number of nucleons, where nucleons is a common term for neutrons and protons.

It is given in the question that number of neutrons is 12, and that the number of protons is same as neutrons. Therefore number of protons is also 12. The mass number A of the given element is given by:

Mass Number (A) = Number of Neutrons + Number of protons = 12 + 12 =24

As number of protons in the atom of the element is 12, its atomic number is also 12. The element corresponding to atomic number 12 as per the periodic table is Magnesium with chemical symbol Mg. It belongs to the "alkali earth metals" of the periodic table.

The electrons in the magnisums atom are configured as follows.

Shell 1 or Shell K: 2

Shell 2 or Shell L: 8

Shell 3 or Shell M: 2

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