# Atomic Mass Of Helium

#### Learning Objective

• Calculate the average atomic mass of an element given its isotopes and their natural abundance The atomic mass number of Carbon is 12 amu, the proton number is 6, and it has no charge. In neutral atoms, the charge is omitted. Above is the atomic symbol for helium from the periodic table, with the atomic number, elemental symbol, and mass indicated. Subscribe Now:More:is atomic number two on.

#### Key Points • An element can have differing numbers of neutrons in its nucleus, but it always has the same number of protons. The versions of an element with different neutrons have different masses and are called isotopes.
• The average atomic mass for an element is calculated by summing the masses of the element’s isotopes, each multiplied by its natural abundance on Earth.
• When doing any mass calculations involving elements or compounds, always use average atomic mass, which can be found on the periodic table.

#### Terms

• natural abundanceThe abundance of a particular isotope naturally found on the planet.
• average atomic massThe mass calculated by summing the masses of an element’s isotopes, each multiplied by its natural abundance on Earth.
• mass numberThe total number of protons and neutrons in an atomic nucleus.

The atomic number of an element defines the element’s identity and signifies the number of protons in the nucleus of one atom. For example, the element hydrogen (the lightest element) will always have one proton in its nucleus. The element helium will always have two protons in its nucleus.

## Isotopes

Atoms of the same element can, however, have differing numbers of neutrons in their nucleus. For example, stable helium atoms exist that contain either one or two neutrons, but both atoms have two protons. These different types of helium atoms have different masses (3 or 4 atomic mass units), and they are called isotopes. For any given isotope, the sum of the numbers of protons and neutrons in the nucleus is called the mass number. This is because each proton and each neutron weigh one atomic mass unit (amu). By adding together the number of protons and neutrons and multiplying by 1 amu, you can calculate the mass of the atom. All elements exist as a collection of isotopes. The word ‘isotope’ comes from the Greek ‘isos’ (meaning ‘same’) and ‘topes’ (meaning ‘place’) because the elements can occupy the same place on the periodic table while being different in subatomic construction.

## Calculating Average Atomic Mass

The average atomic mass of an element is the sum of the masses of its isotopes, each multiplied by its natural abundance (the decimal associated with percent of atoms of that element that are of a given isotope).

Average atomic mass = f1M1 + f2M2 + … + fnMn where f is the fraction representing the natural abundance of the isotope and M is the mass number (weight) of the isotope.

The average atomic mass of an element can be found on the periodic table, typically under the elemental symbol. When data are available regarding the natural abundance of various isotopes of an element, it is simple to calculate the average atomic mass.

• For helium, there is approximately one isotope of Helium-3 for every million isotopes of Helium-4; therefore, the average atomic mass is very close to 4 amu (4.002602 amu).
• Chlorine consists of two major isotopes, one with 18 neutrons (75.77 percent of natural chlorine atoms) and one with 20 neutrons (24.23 percent of natural chlorine atoms). The atomic number of chlorine is 17 (it has 17 protons in its nucleus). ### Atomic Mass Of Helium Atom

To calculate the average mass, first convert the percentages into fractions (divide them by 100). Then, calculate the mass numbers. The chlorine isotope with 18 neutrons has an abundance of 0.7577 and a mass number of 35 amu. To calculate the average atomic mass, multiply the fraction by the mass number for each isotope, then add them together.

Average atomic mass of chlorine = (0.7577 [latex]cdot[/latex] 35 amu) + (0.2423 [latex]cdot[/latex] 37 amu) = 35.48 amu

Another example is to calculate the atomic mass of boron (B), which has two isotopes: B-10 with 19.9% natural abundance, and B-11 with 80.1% abundance. Therefore,

Average atomic mass of boron = (0.199
[latex]cdot[/latex]

### Atomic Mass Of Helium In Kg

10 amu) + (0.801
[latex]cdot[/latex]

11 amu) = 10.80 amu

Whenever we do mass calculations involving elements or compounds (combinations of elements), we always use average atomic masses.

Show Sources

Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:

http://www.boundless.com/
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http://en.wiktionary.org/wiki/mass_number
Wiktionary
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http://www.boundless.com//biology/definition/atomic-mass–2
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http://en.wikipedia.org/wiki/natural%20abundance
Wikipedia
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http://en.wiktionary.org/wiki/isotope
Wiktionary
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### Atomic Mass Of Helium 3

“Introductory Chemistry Online/Measurements and Atomic Structure.”

http://en.wikibooks.org/wiki/Introductory_Chemistry_Online/Measurements_and_Atomic_Structure
Wikibooks
CC BY-SA 3.0.

http://en.wikipedia.org/wiki/Average_atomic_mass
Wikipedia
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### Atomic Mass Of Helium 4 http://en.wikipedia.org/wiki/Atomic_mass
Wikipedia
CC BY-SA 3.0.

“File:Stylised Lithium Atom.svg – Wikipedia, the free encyclopedia.”

http://en.wikipedia.org/w/index.php?title=File:Stylised_Lithium_Atom.svg&page=1
Wikipedia
GNU FDL.

## Specific heat at constant volume, specific heat at constant pressure, specific heat ratio and individual gas constant - R - common gases as argon, air, ether, nitrogen and many more ..

The specific heat (= specific heat capacity) at constant pressure and constant volume processes, and the ratio of specific heats and individual gas constants - R - for some commonly used 'ideal gases', are in the table below (approximate values at 68oF (20oC) and 14.7 psia (1 atm)).

For conversion of units, use the Specific heat online unit converter.

See also tabulated values of specific heat capacity of food and foodstuff, metals and semimetals, common liquids and fluids, common solids and other common substances as well as values of molar heat capacity of common organic substances and inorganic substances.

For full table - rotate the screen!

Gas or VaporFormulaSpecific HeatSpecific Heat RatioIndividual Gas constant
- R -
cp
(kJ/(kg K))
cv
(kJ/(kg K))
cp
(Btu/(lbmoF))
cv
(Btu/(lbmoF))
κ = cp / cvcp - cv
(kJ/(kg K))
cp - cv
(ft lbf/(lbmoR))
Acetone(CH3)2CO1.471.320.350.321.110.15
AcetyleneC2H21.691.370.350.271.2320.31959.34
Air1.010.7180.240.171.400.28753.34
Alcohol (ethanol)C2H5OH1.881.670.450.41.130.22
Alcohol (methanol)CH3OH1.931.530.460.371.260.39
AmmoniaNH32.191.660.520.41.310.5396.5
ArgonAr0.5200.3120.120.071.6670.208
BenzeneC6H61.090.990.260.241.120.1
Blast furnace gas1.030.730.250.171.410.355.05
BromineBr20.250.20.060.051.280.05
ButaneC4H101.671.530.3950.3561.0940.14326.5
Carbon dioxideCO20.8440.6550.210.161.2890.18938.86
Carbon monoxideCO1.020.720.240.171.400.29755.14
Carbon disulphideCS20.670.550.160.131.210.12
ChlorineCl20.480.360.120.091.340.12
ChloroformCHCl30.630.550.150.131.150.08
Coal gas2.141.59
Combustion products10.24
EthaneC2H61.751.480.390.321.1870.27651.5
Ether (diethyl ether)(C2H5)2O2.011.950.480.471.030.06
EthyleneC2H41.531.230.40.331.2400.29655.08
Chlorodifluoromethane, R-22 CHClF21.18
HeliumHe5.193.121.250.751.6672.08386.3
Hexane C6H141.06
Hydrochloric acid0.7950.567
HydrogenH214.3210.163.422.431.4054.12765.9
Hydrogen ChlorideHCl0.80.570.1910.1351.410.2342.4
Hydrogen SulfideH2S0.2430.1871.3245.2
HydroxylOH1.761.271.3840.489
KryptonKr0.250.151
MethaneCH42.221.700.590.451.3040.51896.4
Methyl ChlorideCH3Cl0.2400.2001.2030.6
Natural Gas2.341.850.560.441.270.579.1
NeonNe1.030.6181.6670.412
Nitric OxideNO0.9950.7180.230.171.3860.277
NitrogenN21.040.7430.250.181.4000.29754.99
Nitrogen tetroxideN2O44.694.61.121.11.020.09
Nitrous oxideN2O0.880.690.210.171.270.1835.1
OxygenO20.9190.6590.220.161.3950.26048.24
PentaneC5H121.07
PropaneC3H81.671.480.390.341.130.18935.0
Propene (propylene)C3H61.51.310.360.311.150.1836.8
Water Vapor
Steam 1 psia. 120 – 600 oF
H2O1.931.460.460.351.320.462
Steam 14.7 psia. 220 – 600 oFH2O1.971.50.470.361.310.46
Steam 150 psia. 360 – 600 oFH2O2.261.760.540.421.280.5
Sulfur dioxide (Sulphur dioxide)SO20.640.510.150.121.290.1324.1
XenonXe0.160.097
• κ = cp / cv - the specific heat capacity ratio
• cp = specific heat in a constant pressure process
• cv = specific heat in a constant volume process

For conversion of units, use the Specific heat online unit converter.

See also tabulated values of specific heat of food and foodstuff, metals and semimetals, common liquids and fluids, Common solids and other common substances as well as values of molar heat capacity of common organic substances and inorganic substances.

## Related Topics

• Material Properties - Material properties for gases, fluids and solids - densities, specific heats, viscosities and more
• Thermodynamics - Effects of work, heat and energy on systems

## Related Documents

• Air - Specific Heat at Constant Pressure and Varying Temperature - Online calculator, figures and tables showing how specific heat (Cp and Cv) of dry air vary with temperature at different pressures, SI and imperial units
• Air Specific Heat Ratio - Specific Heat Ratio of air at temperatures from -40 - 1000oC (-40 - 1500oF) at standard atmospheric pressure - Imperial and SI Units
• Argon - Thermophysical Properties - Chemical, Physical and Thermal Properties of Argon
• Compression and Expansion of Gases - Isothermal and isentropic gas compression and expansion processes
• Ethane - Density and Specific Weight - Online calculator, figures and tables showing density and specific weight of ethane, C2H6, at varying temperature and pressure - Imperial and SI Units
• Gases - Dynamic Viscosity - Absolute viscosities of gases
• Gases - Molar Specific Heat - Molar specific heats of gases at constant volume
• Heat Capacity - The heat capacity of a substance is the amount of heat required to change its temperature by one degree, and has units of energy per degree
• Heat, Work and Energy - Heat, work and energy tutorial - essentials as specific heat
• Ideal Gas Law - The relations between volume, pressure, temperature and quantity of a gas, including definition of density of a gas
• Molecular Weight of some Common Substances - Definition and molecular weight (molar mass) of some common substances
• Nitrogen - Specific Heat - Specific heat of Nitrogen Gas - N2 - at temperatures ranging 175 - 6000 K
• Nitrogen - Thermophysical Properties - Chemical, Physical and Thermal Properties of Nitrogen - N2
• Non-ideal gas - Van der Waal's Equation and Constants - Listing of van der Waals constants for more than 200 gases, used to correct for non-ideal behavior of gases caused by intermolecular forces and the volume occupied by the gas particles
• Ratios of Specific Heat of Gases - Ratios of specific heat for gases in constant pressure and volume processes
• Specific Heat - Online Unit Converter - Online specific heat converter with the most commonly used units
• Specific Heat of Solids - Common solids - like brick, cement, glass and many more - and their specific heats - in Imperial and SI units
• Specific Heat of some Liquids and Fluids - Specific heat for some common liquids and fluids - acetone, oil, paraffin, water and many more
• Sulfur Dioxide Liquid - Thermal Properties - Density, specific heat, thermal conductivity and more
• Total and partial pressure - Dalton's law of partial pressures - How to calculate total pressure and partial pressures for gas mixtures from Ideal Gas Law

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