Element with Mass No. 81

The element with mass number 81 refers to the total number of protons and neutrons in the atomic nucleus of the atom. To determine the symbol of this element, we need to consider the relationship between the number of protons and neutrons.

Protons and Neutrons

Protons and neutrons are subatomic particles found in the nucleus of an atom. Protons have a positive charge, while neutrons have no charge and are neutral. The number of protons in an atom determines its atomic number, which is denoted by the symbol Z. The sum of protons and neutrons gives the mass number, denoted by the symbol A.

Calculating Neutrons

To calculate the number of neutrons in an atom, we subtract the number of protons from the mass number. In this case, the element has a mass number of 81 and contains 31.7% more neutrons compared to protons.

Let's assume the number of protons is x. Since the element has 31.7% more neutrons, the number of neutrons can be expressed as 1.317x.

The mass number (A) is the sum of protons (Z) and neutrons:
A = Z + N

Substituting the values, we have:
81 = x + 1.317x

Simplifying the equation:
81 = 2.317x

Dividing both sides by 2.317:
x ≈ 35

Symbol of the Atom

The atomic symbol of an element is represented by a one- or two-letter abbreviation. The number of protons in an atom determines its atomic number and, consequently, its position in the periodic table. In this case, the element has approximately 35 protons.

Referring to the periodic table, we find that the element with 35 protons is bromine (Br). Therefore, the symbol of the atom with a mass number of 81 and containing 31.7% more neutrons compared to protons is Br-81.

Please check the periodic table