An element has an atomic number 15 and mass number 31. What will be thedistribution of electrons in its different shells and the nuclear composition of theatom?

To determine the distribution of electrons in the different shells of an element with atomic number 15, we need to understand the electron configuration. The atomic number represents the number of protons in the nucleus, which is also equal to the number of electrons in a neutral atom.

The electron configuration of an element can be determined by using the Aufbau principle, which states that electrons fill the lowest energy levels first. The first shell can hold a maximum of 2 electrons, the second shell can hold a maximum of 8 electrons, and the third shell can hold a maximum of 8 electrons as well.

Since the atomic number of the element is 15, we can distribute the electrons as follows:

• The first shell will have 2 electrons.
• The second shell will have 8 electrons.
• The remaining 5 electrons will be placed in the third shell.

Now, let's move on to the nuclear composition of the atom. The mass number of an element represents the total number of protons and neutrons in the nucleus. Since the atomic number is 15, which represents the number of protons, we can subtract the atomic number from the mass number to find the number of neutrons.

In this case, the mass number is 31, and the atomic number is 15. Therefore, the number of neutrons can be calculated as:

Number of neutrons = Mass number - Atomic number = 31 - 15 = 16

So, the nuclear composition of the atom will consist of 15 protons, 16 neutrons, and 15 electrons distributed in the different shells as mentioned earlier.