Atomic Mass Flashcards
Memorise the atomic mass of elements to two decimal places.
Give the atomic mass.
(2 d.p)
1.01
Hydrogen is the lightest element and has three isotopes: protium, deuterium, and tritium.
The atomic mass in atomic mass units (amu) reflects the different naturally occurring stable isotopes of an element, including hydrogen’s three isotopes.
Give the atomic mass.
(2 d.p)
4.00
Helium-4 is the most abundant and stable isotope of helium, it makes up 99.9999% of helium’s natural abundance.
Give the atomic mass.
(2 d.p)
6.94
Lithium is a light, soft metal with two stable isotopes: lithium-6 and lithium-7. Its atomic mass reflects the isotopic composition, with lithium-7 making up the majority of its natural abundance.
Give the atomic mass.
(2 d.p)
9.01
Beryllium is a relatively rare element and has a high melting point. It has only one stable isotope, beryllium-9.
Give the atomic mass.
(2 d.p)
10.81
Boron is a metalloid used in various industrial applications. Its atomic mass accounts for its isotopic composition, primarily B-10 and B-11.
Give the atomic mass.
(2 d.p)
12.01
Carbon’s atomic mass includes the average mass contributions of its isotopes, primarily carbon-12 and carbon-13. Its isotopic composition consists of three isotopes: C-12, C-13, and C-14.
Give the atomic mass.
(2 d.p)
14.01
Nitrogen makes up a significant portion of the Earth’s atmosphere in its diatomic gas form.
The atomic mass considers the different isotopes of nitrogen, of which it has two, N-14 and N-15.
Give the atomic mass.
(2 d.p)
16.00
Oxygen is a vital element for sustaining life and is abundant in the Earth’s crust. Its atomic mass accounts for its isotopic composition, which includes three isotopes: O-16, O-17, and O-18.
Give the atomic mass.
(2 d.p)
19.00
Fluorine is a highly reactive and toxic halogen element. Its atomic mass is based on its single stable isotope, F-19.
Give the atomic mass.
(2 d.p)
20.18
Neon has three key isotopes, Ne-20, Ne-21, and Ne-22, with Ne-20 by far being the most abundant (around 90%). It is an unreactive element and classified as a noble gas.
Give the atomic mass.
(2 d.p)
22.99
Sodium is a highly reactive alkali metal commonly found in salts.
The atomic mass accounts for the isotopic composition of sodium, of which its key stable one is Na-23.
Give the atomic mass.
(2 d.p)
24.31
Magnesium is a lightweight and versatile metal used in various industries. The atomic mass considers the three different isotopes of magnesium, Mg-24, Mg-25, and Mg-26.
Give the atomic mass.
(2 d.p)
26.98
Aluminium is a lightweight and malleable metal commonly used in various industries. It is the most abundant metal in the Earth’s crust.
Give the atomic mass.
(2 d.p)
28.09
Silicon is a crucial element in the semiconductor industry due to its properties, itis widely used in electronic devices and solar panels.
Give the atomic mass.
(2 d.p)
30.97
Phosphorus is an essential nutrient for plants and animals, it plays a crucial role in various biological processes.
Give the atomic mass.
(2 d.p)
32.06
Sulphur is a nonmetallic element commonly used in the production of sulfuric acid.
It is known for its distinct smell and is present in various minerals.
Give the atomic mass.
(2 d.p)
35.45
Chlorine is a highly reactive element and a crucial component in disinfectants, commonly used in water treatment and as a bleaching agent.
Give the atomic mass.
(2 d.p)
39.95
Argon is an inert gas commonly used in lightbulbs and welding.
It has three isotopes, with Ar-40 being by far the most abundant.
Give the atomic mass.
(2 d.p)
39.10
Potassium is an essential nutrient for plants and animals and plays a role in nerve function. It has three naturally occurring isotopes, with K-39 being the most abundant.
Give the atomic mass.
(2 d.p)
40.08
Calcium is a vital mineral for the formation and maintenance of healthy bones and teeth.
It is essential for muscle contractions and blood clotting.
Give the atomic mass.
(2 d.p)
44.96
Scandium is a transition metal used in the aerospace and electronic industries.
Scandium alloys are used in high-end lightweight bicycle frames and sports equipment.
Give the atomic mass.
(2 d.p)
47.87
Titanium is a strong, lightweight metal widely used in the aerospace and medical industries. Titanium(IV) oxide is commonly used as a white pigment in paints and cosmetics.
Give the atomic mass.
(2 d.p)
50.94
Vanadium is often used as an alloying element in the production of high-strength steel.
It has two naturally-occuring isotopes, V-50 (minor) and V-51 (major).
Give the atomic mass.
(2 d.p)
52.00
Chromium is commonly used as a coating for automotive parts and in stainless steel production.
Chromium compounds are used in dyes, pigments, and tanning agents.
Give the atomic mass.
(2 d.p)
54.94
Manganese is an essential element for the proper functioning of certain enzymes.
It is used in steel production and as a component in some batteries.
Give the atomic mass.
(2 d.p)
55.85
Iron is a widely used metal known for its strength, versatility, and abundance in the Earth’s crust. It has four naturally occurring isotopes, with Fe-56 being the most abundant.
Give the atomic mass.
(2 d.p)
58.93
Cobalt is often used in the production of magnets and rechargeable batteries.
Cobalt compounds are used in the production of blue pigments and as a catalyst.
Give the atomic mass.
(2 d.p)
58.69
Nickel is a silver-white metal often used in stainless steel production, and it is also commonly used in manufacturing batteries and currency coins.
Give the atomic mass.
(2 d.p)
63.55
Copper is a widely used metal known for its excellent electrical conductivity, it is used in electrical wiring, plumbing, and the production of coins.
Give the atomic mass.
(2 d.p)
65.38
Zinc is a bluish-white metal commonly used as a protective coating for iron and steel.
It has five naturally-occuring isotopes, with Zn-64 being the most abundant.
Give the atomic mass.
(2 d.p)
69.72
Gallium is a soft, silvery metal often used in semiconductors and LEDs. Gallium compounds are also used in medical imaging and as a heat transfer fluid.
Give the atomic mass.
(2 d.p)
72.63
Germanium is a grayish-white metalloid used in semiconductor production, though other materials are becoming more popular for this use. It has five naturally occurring isotopes, with Ge-72 being the most abundant.
Give the atomic mass.
(2 d.p)
74.92
Arsenic is a toxic metalloid used in the production of semiconductors and formerly in pesticides, a use largely discontinued in places like the USA. Of its 33 known isotopes, only one is stable and naturally occurring: As-75.
Give the atomic mass.
(2 d.p)
78.97
Selenium is a semi-metal commonly used in the production of photovoltaic cells and glass. It has six naturally occurring isotopes (Se-74, Se-76, Se-77, Se-78, Se-80, Se-82), five of which are stable. The most abundant isotope is Se-80.
Give the atomic mass.
(2 d.p)
79.90
Bromine is a reddish-brown liquid halogen used in flame retardants and water disinfection (non-drinking purposes like pool water).
It has two naturally occurring stable isotopes, Br-79 and Br-81, which are relatively equal in abundance.
Give the atomic mass.
(2 d.p)
83.80
Krypton is a noble gas often used in specialized lighting and laser applications. It has 32 known isotopes, of which only six are stable: Kr-78, Kr-80, Kr-82, Kr-83, Kr-84, and Kr-86.
Give the atomic mass.
(2 d.p)
85.47
Rubidium is a soft and silvery-white alkali metal with similar physicochemical properties to potassium.
Rb-85 and Rb-87 are rubidium’s stable, naturally-occurring isotopes, with Rb-85 being by far the most abundant (72.17%).
Give the atomic mass.
(2 d.p)
87.62
Strontium is an alkaline-earth metal commonly used in pyrotechnic compounds.
It has four naturally occurring stable isotopes (Sr-84, Sr-86, Sr-87, Sr-88). However, its radioisotope Sr-90 is infamous for being a byproduct of nuclear fallouts and its carcinogenic effects.
Give the atomic mass.
(2 d.p)
88.91
Yttrium is a transition metal often used in high-temperature superconductors (as the YBCO compound) and lasers. Among its many isotopes, Y-89 is the only naturally occurring and stable one, making it monoisotopic.
Give the atomic mass.
(2 d.p)
91.22
Zirconium is a corrosion-resistant metal primarily used in nuclear reactors and sometimes in dental implants.
It has five naturally occurring stable isotopes (Zr-90, Zr-91, Zr-92, Zr-94, Zr-96), with Zr-90 being the most abundant.
Give the atomic mass.
(2 d.p)
92.91
Niobium is a transition metal used in alloys for superconducting magnets and in the aerospace industry.
Nb-93 is the only stable and naturally-occurring isotope of niobium.
Give the atomic mass.
(2 d.p)
95.95
Molybdenum is a transition metal used in high-strength alloys and as a catalyst.
It has seven naturally occurring stable isotopes (Mo-92, Mo-94, Mo-95, Mo-96, Mo-97, Mo-98, Mo-100), with Mo-98 being the most abundant at 24.39%.
Give the atomic mass.
[98]
Technetium is a radioactive element used in medical imaging and as a tracer in research.
It is a synthetic transition metal, indicated by its atomic mass being a whole number in brackets.
This is because atomic mass is based on naturally occurring isotopes and their abundances, so elements with only unstable radioisotopes have an estimated atomic mass.
Give the atomic mass.
(2 d.p)
101.07
Ruthenium is a hard and corrosion-resistant transition metal used in electrical contacts and catalysts.
It has 7 stable, naturally-occurring isotopes (Ru-96 , 98 , 99 , 100 , 101 , 102 , 104), and Ru-102 is the most abundant.
Give the atomic mass.
(2 d.p)
102.91
Rhodium is a rare and precious metal used primarily in catalytic converters and as a coating on optical fibers and mirrors.
Rh-103 is its only stable, naturally occurring isotope, making it monoisotopic.
Give the atomic mass.
(2 d.p)
106.42
Palladium is a precious metal used in catalytic converters, electronics, and jewelry.
It has 6 stable, naturally-occurring isotopes (Pd-102 , 104 , 105 , 106 , 108 , 110).
Give the atomic mass.
(2 d.p)
107.87
Silver is a precious metal known for its high electrical conductivity and lustrous appearance.
Ag-107 and Ag-109 are the stable and naturally-occurring isotopes of silver.
Give the atomic mass.
(2 d.p)
112.41
Cadmium is a toxic metal used in batteries, pigments, and electroplating, but it is regulated due to its teratogenic and carcinogenic properties.
It has eight stable, naturally occurring isotopes, with Cd-114 and Cd-112 being the most abundant.
Give the atomic mass.
(2 d.p)
114.82
Indium is a soft, silvery metal used in semiconductors and liquid crystal displays (LCDs) as indium tin oxide (ITO). In-115 is the most abundant of its two stable, naturally occurring isotopes, the other being In-113.
Give the atomic mass.
(2 d.p)
118.71
Tin has 10 naturally-occurring, stable isotopes, with Sn-120 being the most abundant (32.58%).
The second most abundant isotope of tin is Sn-118 (24.22%).
Give the atomic mass.
(2 d.p)
121.76
Antimony is a silvery, brittle semi-metal often used in alloys to increase their strength. The most stable naturally occurring isotope is Sb-121, with Sb-123 also being quite abundant at 42.79%.
Give the atomic mass.
(2 d.p)
127.60
Tellurium is a semi-metal usually obtained as a grey powder, often alloyed with lead to improve hardness and resistance to acids. Te-130 is its most abundant natural isotope, closely followed by Te-128, among its eight stable isotopes.
Give the atomic mass.
(2 d.p)
126.90
Iodine is a monoisotopic element with one stable isotope, I-127. It also has a naturally occurring radioactive isotope, I-129, along with 32 other radioactive isotopes.
Iodine is a halogen commonly used as a disinfectant and as an additive to salt in regions with low soil iodine content, such as New Zealand.
Give the atomic mass.
(2 d.p)
131.29
Xenon is a colorless, odorless noble gas and very unreactive.
It is used in specialised lighting sources.
Xenon-129 and Xe-132 are xenon’s most stable and abundant isotopes of the 9 naturally-occurring ones.
Give the atomic mass.
(2 d.p)
132.91
Caesium is a soft, gold-coloured alkali metal that reacts explosively with water, it has a single stable, naturally-occurring isotope, Cs-133.
Give the atomic mass.
(2 d.p)
137.33
Barium is a soft, silvery metal that rapidly tarnishes in air and reacts with water. The most common naturally-occurring and stable isotope of barium’s 7, is Ba-138.
Give the atomic mass.
(2 d.p)
138.91
Lanthanum is a silvery-white lanthanide metal that tarnishes in air and burns easily once ignited.
Its most abundant isotope is La-139, with La-138 also occurring naturally in much smaller amounts.
Give the atomic mass.
(2 d.p)
140.12
Cerium is a grey lanthanide metal that is easily tarnished, reactive with water, and burns easily when heated.
The most abundant isotope of cerium is Ce-140 of its 4 naturally-occurring, stable ones.
Give the atomic mass.
(2 d.p)
140.91
Praseodymium is a soft, silvery lanthanide metal. Pr-141 is praseodymium’s only naturally-occurring and stable isotope.
Give the atomic mass.
(2 d.p)
144.24
Neodymium is a silvery-white lanthanide metal that rapidly tarnishes in air.
The most abundant of neodymium’s 7 naturally-occurring, stable isotopes is Nd-142.
Give the atomic mass.
[145]
Promethium is a synthetic (artificially-produced) lanthanide metal, which is indicated by its atomic mass being commonly represented as a whole-number contained within square brackets.
This is because atomic mass is based on naturally-occurring isotopes and their abundances, and so elements with only unstable radioisotopes have an estimated atomic mass.
Give the atomic mass.
(2 d.p)
150.36
Samarium is a silvery-white lanthanide metal. The most abundant of samarium’s 7 naturally-occurring, stable isotopes is Sm-152.
Give the atomic mass.
(2 d.p)
151.96
Europium is a silvery, soft lanthanide metal that easily tarnishes and reacts with water. Of its two naturally occurring stable isotopes, Eu-153 is the most abundant, closely followed by Eu-151.
Give the atomic mass.
(2 d.p)
157.25
Gadolinium is a soft, silvery lanthanide metal that reacts with water and oxygen.
The most abundant of gadolinium’s 7 naturally-occurring, stable isotopes is Gd-158.
Give the atomic mass.
(2 d.p)
158.93
Terbium is a soft, silvery lanthanide metal. Its only naturally occurring stable isotope is Tb-159, making it monoisotopic.
Give the atomic mass.
(2 d.p)
162.50
Dysprosium is a bright, silvery lanthanide metal.
The most abundant of dysprosium’s 7 naturally-occurring, stable isotopes is Dy-164.
Give the atomic mass.
(2 d.p)
164.93
Holmium is a bright, silvery lanthanide metal. Its only naturally occurring stable isotope is Ho-165, making it monoisotopic.
Give the atomic mass.
(2 d.p)
167.26
Erbium is a soft, silvery lanthanide metal. The most abundant of its six naturally occurring stable isotopes is Er-166.
Give the atomic mass.
(2 d.p)
174.97
Lutetium is a silvery-white, dense, hard lanthanide metal. The most abundant of its two naturally occurring stable isotopes is Lu-175, making up 97.40%.
Give the atomic mass.
(2 d.p)
168.93
Thulium is a bright, silvery lanthanide metal. Its only naturally occurring stable isotope is Tm-169, making it monoisotopic.
Give the atomic mass.
(2 d.p)
173.05
Ytterbium is a soft, silvery lanthanide metal that slowly oxidises in air, forming a protective outer-layer.
The most abundant of Ytterbium’s 7 naturally-occurring, stable isotopes is Yb-174.
Give the atomic mass.
(2 d.p)
178.49
Hafnium is a lustrous, silvery transition metal that is ductile and resistant to corrosion.
The most abundant of hafnium’s 6 naturally-occurring, stable isotopes is Hf-180.
Give the atomic mass.
(2 d.p)
180.95
Tantalum is a lustrous, silvery transition metal that is resistant to corrosion. The most abundant of tantalum’s 2 naturally-occurring, stable isotopes is undeniably Ta-181 (99.988%).
Give the atomic mass.
(2 d.p)
183.84
Tungsten is a lustrous, silvery-white transition metal. The most abundant of tungsten’s 5 naturally-occurring, stable isotopes is W-184.
Give the atomic mass.
(2 d.p)
186.21
Rhenium is a transition metal with the second-highest melting point among metallic elements. Its most abundant naturally occurring stable isotope is Re-187.
Give the atomic mass.
(2 d.p)
190.23
Osmium is a lustrous, silvery metal that is resistant to corrosion and is the densest amongst all elements.
The most abundant of osmium’s 7 naturally-occurring, stable isotopes is Os-192.
Give the atomic mass.
(2 d.p)
192.22
Iridium is a high-density, hard, silvery transition metal with a high melting point and is nearly as unreactive as gold. The most abundant of its two naturally occurring stable isotopes is Ir-193.
Give the atomic mass.
(2 d.p)
195.08
Platinum is a shiny, silvery-white transition metal that is as resistant to corrosion as gold. Among its six naturally occurring stable isotopes, Pt-195 is the most abundant, followed closely by Pt-194.
Give the atomic mass.
(2 d.p)
196.97
Gold is a precious transition metal renowned for its beauty and resistance to corrosion.
Au-197 is gold’s one stable isotope, but it also has many more known radioisotopes.
Give the atomic mass.
(2 d.p)
200.59
Mercury is a silvery, heavy transition metal that exists as a liquid at room temperature.
It has seven naturally occurring stable isotopes (Hg-196, Hg-198, Hg-199, Hg-200, Hg-201, Hg-202, Hg-204), with Hg-202 being the most abundant.
Give the atomic mass.
(2 d.p)
204.38
Thallium is a soft, silvery-white post-transition metal that easily tarnishes.
The most abundant of thallium’s 2 naturally-occurring, stable isotopes is Tl-205 by far (70.48%).
Give the atomic mass.
(2 d.p)
207.20
Lead is a soft, dull, silvery-grey, and toxic post-transition metal. It has four naturally occurring stable isotopes (Pb-204, Pb-206, Pb-207, Pb-208) and many other radioisotopes, with Pb-208 being the most abundant.
Give the atomic mass.
(2 d.p)
208.98
Bismuth is a high-density, silvery, pink-tinged post-transition metal. Its only naturally occurring stable isotope is Bi-209, making it monoisotopic.
Give the atomic mass.
[209]
Polonium is a silvery-grey, radioactive metalloid that is mostly synthetic, as indicated by its atomic mass being represented as a whole number in brackets.
It does occur naturally in minute quantities in uranium ores, but it is uneconomical to extract.
Give the atomic mass.
[210]
Astatine is a dangerously radioactive, synthetic halogen and the heaviest in its group.
Its atomic mass is given as a whole number in brackets because it has only unstable radioisotopes, so its mass is estimated.
Give the atomic mass.
[222]
Radon is a colorless, odorless, and chemically inert but radioactive noble gas.
It forms from the decay of radium-226 and has no stable isotopes, so its atomic mass is given as a whole number in brackets, indicating an estimated value.
Give the atomic mass.
[223]
Francium is intensely radioactive and the heaviest alkali metal. It is mostly synthetic but can occur briefly in small quantities from radioactive decay.
Since atomic mass is based on naturally occurring isotopes and their abundances, elements with only unstable radioisotopes have an estimated atomic mass shown in brackets.
Give the atomic mass.
[226]
Radium is a soft, lustrous, silvery radioactive alkaline-earth metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[227]
Actinium is a soft, silvery-white, radioactive actinide metal that glows blue in the dark.
It has no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
(2 d.p)
232.04
Thorium is a naturally occurring, silvery, and weakly radioactive actinide metal. Its only naturally occurring and relatively stable isotope is Th-232, making it monoisotopic.
Give the atomic mass.
(2 d.p)
231.04
Protactinium is a rare, silvery, and highly radioactive actinide metal. It has naturally occurring isotopes but no stable ones, with Pa-231 being the most abundant.
These isotopes allow for a standard atomic mass to be derived, so its value is not presented in brackets.
Give the atomic mass.
[237]
Neptunium has no stable isotopes, which is indicated by its atomic mass being commonly represented as a whole-number contained within square brackets.
Give the atomic mass.
(2 d.p)
238.03
Uranium is a dense, silvery actinide metal and the heaviest naturally occurring element.
It has naturally occurring isotopes but no stable ones, with U-238 being the most abundant.
These isotopes allow for a standard atomic mass to be derived, so its value is not presented in brackets.
Give the atomic mass.
[244]
Plutonium has no stable isotopes, which is indicated by its atomic mass being commonly represented as a whole-number contained within square brackets.
Give the atomic mass.
[243]
Americium is a lustrous, silvery, radioactive actinide metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[247]
Curium has no stable isotopes, which is indicated by its atomic mass being commonly represented as a whole-number contained within square brackets.
Give the atomic mass.
[247]
Berkelium is a silvery, radioactive transuranium actinide metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[251]
Californium is a radioactive actinide metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[252]
Einsteinium is a radioactive transuranium actinide metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[257]
Fermium is a synthetic, radioactive actinide metal.
It has no stable isotopes, which is indicated by its atomic mass being commonly represented as a whole-number contained within square brackets.
Give the atomic mass.
[258]
Mendelevium is a synthetic, radioactive actinide metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[259]
Nobelium is a synthetic, radioactive actinide metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[262]
Lawrencium is a radioactive, synthetic actinide metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[267]
Rutherfordium is a synthetic, highly radioactive transuranic element with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[268]
Dubnium is a radioactive, synthetic transuranium metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[269]
Seaborgium is a synthetic, radioactive transuranic metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[270]
Bohrium is a synthetic, highly radioactive transuranic element with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[269]
Hassium is a synthetic transuranic element whose most stable isotope has a half-life of about 9.7 seconds. It has no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[278]
Meitnerium is a synthetic, highly radioactive transuranic element with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[281]
Darmstadtium is a highly radioactive, synthetic transuranium metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[282]
Roentgenium is a synthetic, highly unstable transuranium element with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[285]
Copernicium is a synthetic, highly radioactive transuranic element with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[286]
Nihonium is a synthetic and highly radioactive transuranium metal.
It has no stable isotopes, which is indicated by its atomic mass being commonly represented as a whole-number contained within square brackets.
Give the atomic mass.
[289]
Flerovium is a synthetic and highly radioactive transuranium metal.
It has no stable isotopes, which is indicated by its atomic mass being commonly represented as a whole-number contained within square brackets.
Give the atomic mass.
[290]
Moscovium is a synthetic, highly radioactive transuranium metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[293]
Livermorium is a synthetic and highly radioactive transuranium metal.
It has no stable isotopes, which is indicated by its atomic mass being commonly represented as a whole-number contained within square brackets.
Give the atomic mass.
[294]
Tennessine is a synthetic, highly radioactive transuranium element in the halogen group. It has no stable isotopes, so its atomic mass is represented as a whole number in brackets.
Give the atomic mass.
[294]
Oganesson is a synthetic, highly radioactive transuranium metal with no stable isotopes, so its atomic mass is represented as a whole number in brackets.
