Question #a8865

Stacked numbers are used in isotope notation to convey information about an isotope's atomic number and mass number.

As you can see, the atomic number, #Z#, which tells you the number of protons that are present in the nucleus, is added to the bottom left of the chemical symbol.

Stacked on top of it is the mass number, #A#, which tells you the number of protons and neutrons present inside the nucleus. If you take #N# to be the number of neutrons present inside the nucleus, you can say that

#color(blue)(|bar(ul(color(white)(a/a)A = Z + N color(white)(a/a)|)))#

This means that the number of neutrons present inside the nucleus can be calculated by subtracting the number of protons, i.e. the atomic number, from the number of protons and neutrons, i.e. the mass number

#N =A - Z#

Here's an example of how to use the isotope notation. Let's say that you want to determine the number of neutrons present inside the nucleus of a carbon-14 atom, #""_(color(white)(1)color(red)(6))^color(blue)(14)"C"#.

As you can see, the carbon-14 isotope has

#Z = color(red)(6)" "# and #" "A = color(blue)(14)#

This means that you have

#N = 14 - 8 = "8 neutrons"#

Therefore, you can say that a #""_(color(white)(1)color(red)(6))^color(blue)(14)"C"# atom contains #8# neutrons inside its nucleus.