Question #b1ea6

Isotope notation allows you to identify various isotopes by using atomic number, #Z#, chemical symbol, and mass number, #A#.

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So, let's start with antimony-125. Grab a periodic table and look for antimony, #"Sn"#. You'll find it located in period 5, group 14.

Antimony has an atomic number equal to #50#, which means that any atom that contains #50# protons in its nucleus will be an atom of antimony.

Since you know that the given isotope has a mass number equal to #125#, you can say that its isotope notation will be

#color(green)(|bar(ul(color(white)(a/a)color(black)(""_(color(white)(a)50)^125"Sn")color(white)(a/a)|))) -># antimony-125

Next up, a bismuth nucleus that contains #120# neutrons. Look for bismuth, #"Bi"#, in the periodic table. You'll find it located in period 6, group 16. Bismuth has an atomic number of #83#, which tells you that its nucleus contains #83# protons.

No,w to get he mass number of this isotope, add the number of protons and the number of neutrons located in the nucleus

#A = Z + N#

#A = 83 + 120 = 203#

The isotope notation for this particular isotope will thus be

#color(green)(|bar(ul(color(white)(a/a)color(black)(""_(color(white)(a)83)^203"Bi")color(white)(a/a)|))) -># bismuth-203

Finally, a nucleus of element 35 that contains #46# neutrons. Once again, pick the a periodic table and look for the element that has an atomic number equal to #35#.

You'll find that this element is bromine, #"Br"#, located in period 4, group 17.

Calculate the isotope's mass number by using the number of protons and the number of neutrons it contains in its nucleus

#A = 35 + 46 = 81#

The isotope notation for this isotope will be

#color(green)(|bar(ul(color(white)(a/a)color(black)(""_ 35^81"Br")color(white)(a/a)|))) -># bromine-81