# 1.1 Atomic structure and symbolism  (Page 4/18)

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Information about the naturally occurring isotopes of elements with atomic numbers 1 through 10 is given in [link] . Note that in addition to standard names and symbols, the isotopes of hydrogen are often referred to using common names and accompanying symbols. Hydrogen-2, symbolized 2 H, is also called deuterium and sometimes symbolized D. Hydrogen-3, symbolized 3 H, is also called tritium and sometimes symbolized T.

Nuclear Compositions of Atoms of the Very Light Elements
Element Symbol Atomic Number Number of Protons Number of Neutrons Mass (amu) % Natural Abundance
hydrogen ${}_{1}^{1}\text{H}$
(protium)
1 1 0 1.0078 99.989
${}_{1}^{2}\text{H}$
(deuterium)
1 1 1 2.0141 0.0115
${}_{1}^{3}\text{H}$
(tritium)
1 1 2 3.01605 — (trace)
helium ${}_{2}^{3}\text{He}$ 2 2 1 3.01603 0.00013
${}_{2}^{4}\text{He}$ 2 2 2 4.0026 100
lithium ${}_{3}^{6}\text{Li}$ 3 3 3 6.0151 7.59
${}_{3}^{7}\text{Li}$ 3 3 4 7.0160 92.41
beryllium ${}_{4}^{9}\text{Be}$ 4 4 5 9.0122 100
boron ${}_{\phantom{\rule{0.5em}{0ex}}5}^{10}\text{B}$ 5 5 5 10.0129 19.9
${}_{\phantom{\rule{0.5em}{0ex}}5}^{11}\text{B}$ 5 5 6 11.0093 80.1
carbon ${}_{\phantom{\rule{0.5em}{0ex}}6}^{12}\text{C}$ 6 6 6 12.0000 98.89
${}_{\phantom{\rule{0.5em}{0ex}}6}^{13}\text{C}$ 6 6 7 13.0034 1.11
${}_{\phantom{\rule{0.5em}{0ex}}6}^{14}\text{C}$ 6 6 8 14.0032 — (trace)
nitrogen ${}_{\phantom{\rule{0.5em}{0ex}}7}^{14}\text{N}$ 7 7 7 14.0031 99.63
${}_{\phantom{\rule{0.5em}{0ex}}7}^{15}\text{N}$ 7 7 8 15.0001 0.37
oxygen ${}_{\phantom{\rule{0.5em}{0ex}}8}^{16}\text{O}$ 8 8 8 15.9949 99.757
${}_{\phantom{\rule{0.5em}{0ex}}8}^{17}\text{O}$ 8 8 9 16.9991 0.038
${}_{\phantom{\rule{0.5em}{0ex}}8}^{18}\text{O}$ 8 8 10 17.9992 0.205
fluorine ${}_{\phantom{\rule{0.5em}{0ex}}9}^{19}\text{F}$ 9 9 10 18.9984 100
neon ${}_{10}^{20}\text{Ne}$ 10 10 10 19.9924 90.48
${}_{10}^{21}\text{Ne}$ 10 10 11 20.9938 0.27
${}_{10}^{22}\text{Ne}$ 10 10 12 21.9914 9.25

## Atomic mass

Because each proton and each neutron contribute approximately one amu to the mass of an atom, and each electron contributes far less, the atomic mass    of a single atom is approximately equal to its mass number (a whole number). However, the average masses of atoms of most elements are not whole numbers because most elements exist naturally as mixtures of two or more isotopes.

The mass of an element shown in a periodic table or listed in a table of atomic masses is a weighted, average mass of all the isotopes present in a naturally occurring sample of that element. This is equal to the sum of each individual isotope’s mass multiplied by its fractional abundance.

$\text{average mass}=\sum _{i}{\left(\text{fractional abundance}\phantom{\rule{0.2em}{0ex}}×\phantom{\rule{0.2em}{0ex}}\text{isotopic mass}\right)}_{i}$

For example, the element boron is composed of two isotopes: About 19.9% of all boron atoms are 10 B with a mass of 10.0129 amu, and the remaining 80.1% are 11 B with a mass of 11.0093 amu. The average atomic mass for boron is calculated to be:

$\begin{array}{cc}\hfill \text{boron average mass}& =\left(0.199\phantom{\rule{0.2em}{0ex}}×\phantom{\rule{0.2em}{0ex}}\text{10.0129 amu}\right)+\left(0.801\phantom{\rule{0.2em}{0ex}}×\phantom{\rule{0.2em}{0ex}}\text{11.0093 amu}\right)\hfill \\ & =\text{1.99 amu}+\text{8.82 amu}\hfill \\ & =\text{10.81 amu}\hfill \end{array}$

It is important to understand that no single boron atom weighs exactly 10.8 amu; 10.8 amu is the average mass of all boron atoms, and individual boron atoms weigh either approximately 10 amu or 11 amu.

## Calculation of average atomic mass

A meteorite found in central Indiana contains traces of the noble gas neon picked up from the solar wind during the meteorite’s trip through the solar system. Analysis of a sample of the gas showed that it consisted of 91.84% 20 Ne (mass 19.9924 amu), 0.47% 21 Ne (mass 20.9940 amu), and 7.69% 22 Ne (mass 21.9914 amu). What is the average mass of the neon in the solar wind?

## Solution

$\begin{array}{cc}\hfill \text{average mass}& =\left(0.9184\phantom{\rule{0.2em}{0ex}}×\phantom{\rule{0.2em}{0ex}}\text{19.9924 amu}\right)+\left(0.0047\phantom{\rule{0.2em}{0ex}}×\phantom{\rule{0.2em}{0ex}}\text{20.9940 amu}\right)+\left(0.0769\phantom{\rule{0.2em}{0ex}}×\phantom{\rule{0.2em}{0ex}}\text{21.9914 amu}\right)\hfill \\ & =\left(18.36+0.099+1.69\right)\phantom{\rule{0.2em}{0ex}}\text{amu}\hfill \\ & =\text{20.15 amu}\hfill \end{array}$

The average mass of a neon atom in the solar wind is 20.15 amu. (The average mass of a terrestrial neon atom is 20.1796 amu. This result demonstrates that we may find slight differences in the natural abundance of isotopes, depending on their origin.)

A sample of magnesium is found to contain 78.70% of 24 Mg atoms (mass 23.98 amu), 10.13% of 25 Mg atoms (mass 24.99 amu), and 11.17% of 26 Mg atoms (mass 25.98 amu). Calculate the average mass of a Mg atom.

24.31 amu

what's the easiest and fastest way to the synthesize AgNP?
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Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
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Yasmin
what is the function of carbon nanotubes?
Cesar
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
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Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
can nanotechnology change the direction of the face of the world
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the Beer law works very well for dilute solutions but fails for very high concentrations. why?
how did you get the value of 2000N.What calculations are needed to arrive at it
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A teaspoon of the carbohydrate sucrose contains 16 calories, what is the mass of one teaspoo of sucrose if the average number of calories for carbohydrate is 4.1 calories/g?
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