go to the AUS-e-TUTE homepage
home test Join AUS-e-TUTE game contact
 

 

Isotopes

Key Concepts

  • Isotopes are atoms of the same element that have a different number of neutrons in their nuclei.

  • Isotopes of an element will have the same Atomic Number (Z) but a different Mass Number (A):

    Atomic Number (Z) is the number of protons in the nucleus of an atom and is the same for all atoms of the same element.

    Mass Number (A) is the number of protons + the number of neutrons in the nucleus of an atom and will be different for each isotope of an element.

  • A particular isotope of an element can be referred to in a number of ways:

    name-A, eg, carbon-12, carbon-14

    ASymbol, eg, 12C, 14C

    ASymbol
    Z
    eg,
    12C,
    6
    14C,
    6

  • The number of neutrons in the nucleus of an atom can be calculated using the Atomic Number (Z) and the Mass Number (A): A - Z = number of neutrons.

  • Isotopes can be classified as natural (found in nature) or man made (artificial or synthetic).

  • Isotopes can also be classified as stable or unstable:

  1. A stable isotope does NOT undergo radioactive (or nuclear) decay.

  2. An unstable isotope undergoes radioactive (or nuclear) decay.
    Unstable isotopes are also known as radioisotopes or radionucleides

Examples of Naturally Occurring Isotopes

Element Atomic Number (Z)
(= no. protons)
Isotope Mass Number (A)
(= no. protons + no. neutrons)
Number of Neutrons
(A - Z)
hydrogen 1 hydrogen-1,
1H, 11H
1 1 - 1 = 0
hydrogen-2,
2H, 21H
2 2 - 1 = 1
helium 2 helium-3,
3He, 32He
3 3 - 2 = 1
helium-4,
4He, 42He
4 4 - 2 = 2
lithium 3 lithium-6,
6Li, 63Li
3 6 - 3 = 3
lithium-7,
7Li, 73Li
7 7 - 3 = 4
boron 5 boron-10,
10B, 105B
10 10 - 5 = 5
boron-11,
11B, 115B
11 11 - 5 = 6
carbon 6 carbon-12,
12C, 126C
12 12 - 6 = 6
carbon-13,
13C, 136C
13 13 - 6 = 7
carbon-14,
14C, 146C
14 14 - 6 = 8
nitrogen 7 nitrogen-14,
14N, 147N
14 14 - 7 = 7
nitrogen-15,
15N, 157N
15 15 - 7 = 8
oxygen 8 oxygen-16,
16O, 168O
16 16 - 8 = 8
oxygen-17,
17O, 178O
17 17 - 8 = 9
oxygen-18,
18O, 188O
18 18 - 8 = 10
neon 10 neon-20,
20Ne, 2010Ne
20 20 - 10 = 10
neon-21,
21Ne, 2110Ne
21 21 - 10 = 11
neon-22,
22Ne, 2210Ne
22 22 - 10 = 12

Examples of Naturally Occurring Stable and Unstable Isotopes (radioisotopes or radionucleides)

Element Stable Isotope(s) Radioisotope(s)
carbon carbon-12 carbon-14
potassium potassium-39
potassium-41
potassium-40
calcium calcium-40
calcium-42
calcium-43
calcium-44
calcium-46
calcium-48
vanadium vanadium-51 vanadium-50
germanium germanium-70
germanium-72
germanium-73
germanium-74
germanium-76
selenium selenium-74
selenium-74
selenium-76
selenium-77
selenium-78
selenium-80
selenium-82
krypton krypton-80
krypton-82
krypton-83
krypton-84
krypton-86
krypton-78
rubidium rubidium-85 rubidium-87
cadmium cadmium-106
cadmium-108
cadmium-110
cadmium-111
cadmium-112
cadmium-114
cadmium-113
cadmium-116
osmium osmium-184
osmium-187
osmium-188
osmium-189
osmium-190
osmium-192
osmium-186
platinum platinum-192
platinum-194
platinum-195
platinum-196
platinum-198
platinum-190
uranium uranium-234
uranium-235
uranium-238

Examples of Naturally Occurring and Man Made Isotopes

Element Naturally Occurring Isotope(s) Man Made Radioisotope(s)
hydrogen hydrogen-1
hydrogen-2
hydrogen-3
sodium sodium-23 sodium-22
phosphorus phosphorus-31 phosphorus-32
phosphorus-33
chlorine chlorine-35
chlorine-37
chlorine-36
technetium technetium-95
technetium-96
technetium-97
technetium-98
technetium-99
iodine iodine-127 iodine-124
iodine-125
iodine-126
iodine-129
iodine-131
lead lead-204
lead-206
lead-207
lead-208
lead-202
lead-203
lead-205
lead-210

All transuranic elements (those with Atomic Number greater than 92) are man made and unstable.

Examples of transuranic elements:

  • neptunium, 234Np, 235Np, 236Np, 237Np, 238Np, 239Np

  • plutonium, 236Pu, 237Pu, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, 244Pu, 246Pu, 247Pu

  • americium, 240Am, 241Am, 242Am, 243Am

  • curium, 240Cm, 241Cm, 242Cm, 243Cm, 244Cm, 245Cm, 246Cm, 247Cm, 248Cm, 250Cm

  • berkelium, 245Bk, 246Bk, 247Bk,248Bk, 249Bk

  • californium, 246Cf, 248Cf, 249Cf, 250Cf, 251Cf, 252Cf, 253Cf, 254Cf

  • einsteinium, 251Es, 252Es, 253Es, 254Es, 255Es

  • fermium, 252Fm, 253Fm, 257Fm

  • mendelevium, 258Md, 260Md


What would you like to do now?
advertise on the AUS-e-TUTE website and newsletters
 
 

Search this Site

You can search this site using a key term or a concept to find tutorials, tests, exams and learning activities (games).
 

Become an AUS-e-TUTE Member

 

AUS-e-TUTE's Blog

 

Subscribe to our Free Newsletter

Email email us to
subscribe to AUS-e-TUTE's free quarterly newsletter, AUS-e-NEWS.

AUS-e-NEWS quarterly newsletter

AUS-e-NEWS is emailed out in
December, March, June, and September.

 

Ask Chris, the Chemist, a Question

The quickest way to find the definition of a term is to ask Chris, the AUS-e-TUTE Chemist.

Chris can also send you to the relevant
AUS-e-TUTE tutorial topic page.

 
 
 

Share this Page

Bookmark and Share
 
 

© AUS-e-TUTE