Question

For the symbol ${}_2{}^4\mathrm{X}$, identify the element, and write down its atomic number and mass number.

Answer 1

• The general representation of an element = ${}_{\mathrm{Atomic}\mathrm{number}\left(\mathrm{Z}\right)}{}^{\mathrm{Mass}\mathrm{number}\left(\mathrm{A}\right)}\mathrm{X}$
• The given symbol = ${}_2{}^4\mathrm{X}$
• Atomic number refers to the total number of protons present in the nucleus of an atom.
• It is represented by the letter “Z”.
• It is written as a subscript on the left-hand side of the chemical symbol.
• Therefore the atomic number of element $\left({}_2{}^4\mathrm{X}\right)$ = 2
• The total number of protons and neutrons present in the nucleus of an atom is called the mass number.
• It is represented by the letter “A”.
• It is written as a superscript on the left-hand side of the chemical symbol.
• Therefore the mass number of the element $\left({}_2{}^4\mathrm{X}\right)$ = 4
• Name of an element having the atomic number 2 and mass number 4 = $\mathrm{Helium}\left(\mathrm{He}\right)$.