Final answer:
The value of the element at b23 is 23. The element is Boron, with an atomic number of 5 and a mass number of 23.
Step-by-step explanation:
The value of the element at b23 is 23. The letter 'b' indicates the element Boron, which has an atomic number of 5. The number 23 represents the mass number of the isotope of Boron in question. Isotopes are atoms of the same element with different numbers of neutrons, and the mass number represents the sum of the protons and neutrons in the nucleus of an atom.