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Models are often simplified. The small toy cars that you may have played with as a child are models. They give you a good idea of what a real car looks like, but they are much smaller and much simpler. A model cannot always be absolutely accurate and it is important that we realise this so that we don't build up a false idea about something.

In groups of 4-5, you are going to build a model of an atom. Before you start, think about these questions:

  • What information do I know about the structure of the atom? (e.g. what parts make it up? how big is it?)
  • What materials can I use to represent these parts of the atom as accurately as I can?
  • How will I put all these different parts together in my model?

As a group, share your ideas and then plan how you will build your model. Once you have built your model, discuss the following questions:

  • Does our model give a good idea of what the atom actually looks like?
  • In what ways is our model inaccurate ? For example, we know that electrons move around the atom's nucleus, but in your model, it might not have been possible for you to show this.
  • Are there any ways in which our model could be improved?

Now look at what other groups have done. Discuss the same questions for each of the models you see and record your answers.

The following simulation allows you to build an atom
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Build an atom simulation

This is another simulation that allows you to build an atom. This simulation also provides a summary of what you have learnt so far.
Run demo

Build an atom simulation 2


  • Much of what we know today about the atom, has been the result of the work of a number of scientists who have added to each other's work to give us a good understanding of atomic structure.
  • Some of the important scientific contributors include J.J.Thomson (discovery of the electron, which led to the Plum Pudding Model of the atom), Ernest Rutherford (discovery that positive charge is concentrated in the centre of the atom) and Niels Bohr (the arrangement of electrons around the nucleus in energy levels).
  • Because of the very small mass of atoms, their mass is measured in atomic mass units (u). 1 u = 1 , 67 × 10 - 24 g .
  • An atom is made up of a central nucleus (containing protons and neutrons ), surrounded by electrons .
  • The atomic number (Z) is the number of protons in an atom.
  • The atomic mass number (A) is the number of protons and neutrons in the nucleus of an atom.
  • The standard notation that is used to write an element, is Z A X , where X is the element symbol, A is the atomic mass number and Z is the atomic number.
  • The isotope of a particular element is made up of atoms which have the same number of protons as the atoms in the original element, but a different number of neutrons. This means that not all atoms of an element will have the same atomic mass.
  • The relative atomic mass of an element is the average mass of one atom of all the naturally occurring isotopes of a particular chemical element, expressed in atomic mass units. The relative atomic mass is written under the elements' symbol on the Periodic Table.
  • The energy of electrons in an atom is quantised . Electrons occur in specific energy levels around an atom's nucleus.
  • Within each energy level, an electron may move within a particular shape of orbital . An orbital defines the space in which an electron is most likely to be found. There are different orbital shapes, including s, p, d and f orbitals.
  • Energy diagrams such as Aufbau diagrams are used to show the electron configuration of atoms.
  • The electrons in the outermost energy level are called valence electrons .
  • The electrons that are not valence electrons are called core electrons .
  • Atoms whose outermost energy level is full, are less chemically reactive and therefore more stable, than those atoms whose outer energy level is not full.

End of chapter exercises

  1. Write down only the word/term for each of the following descriptions.
    1. The sum of the number of protons and neutrons in an atom
    2. The defined space around an atom's nucleus, where an electron is most likely to be found
  2. For each of the following, say whether the statement is True or False. If it is False, re-write the statement correctly.
    1. 10 20 Ne and 10 22 Ne each have 10 protons, 12 electrons and 12 neutrons.
    2. The atomic mass of any atom of a particular element is always the same.
    3. It is safer to use helium gas rather than hydrogen gas in balloons.
    4. Group 1 elements readily form negative ions.
  3. Multiple choice questions: In each of the following, choose the one correct answer.
    1. The three basic components of an atom are:
      1. protons, neutrons, and ions
      2. protons, neutrons, and electrons
      3. protons, neutrinos, and ions
      4. protium, deuterium, and tritium
    2. The charge of an atom is...
      1. positive
      2. neutral
      3. negative
    3. If Rutherford had used neutrons instead of alpha particles in his scattering experiment, the neutrons would...
      1. not deflect because they have no charge
      2. have deflected more often
      3. have been attracted to the nucleus easily
      4. have given the same results
    4. Consider the isotope 92 234 U . Which of the following statements is true ?
      1. The element is an isotope of 94 234 Pu
      2. The element contains 234 neutrons
      3. The element has the same electron configuration as 92 238 U
      4. The element has an atomic mass number of 92
    5. The electron configuration of an atom of chlorine can be represented using the following notation:
      1. 1 s 2 2 s 8 3 s 7
      2. 1 s 2 2 s 2 2 p 6 3 s 2 3 p 5
      3. 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6
      4. 1 s 2 2 s 2 2 p 5
  4. Give the standard notation for the following elements:
    1. beryllium
    2. carbon-12
    3. titanium-48
    4. fluorine
  5. Give the electron configurations and aufbau diagrams for the following elements:
    1. aluminium
    2. phosphorus
    3. carbon
  6. Use standard notation to represent the following elements:
    1. argon
    2. calcium
    3. silver-107
    4. bromine-79
    Click here for the solution
  7. For each of the following elements give the number of protons, neutrons and electrons in the element:
    1. 78 195 Pt
    2. 18 40 Ar
    3. 27 59 Co
    4. 3 7 Li
    5. 5 11 B
    Click here for the solution
  8. For each of the following elements give the element or number represented by 'x':
    1. 45 103 X
    2. x 35 Cl
    3. 4 x Be
  9. Which of the following are isotopes of 12 24 Mg :
    1. 25 12 Mg
    2. 12 26 Mg
    3. 13 24 Al
  10. If a sample contains 69% of copper-63 and 31% of copper-65, calculate the relative atomic mass of an atom in that sample.
  11. Complete the following table:
    Element Electron configuration Core electrons Valence electrons
    Boron (B)
    Calcium (Ca)
    Silicon (Si)
    Lithium (Li)
    Neon (Ne)
  12. Draw aufbau diagrams for the following elements:
    1. beryllium
    2. sulphur
    3. argon

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
The fundamental frequency of a sonometer wire streached by a load of relative density 's'are n¹ and n² when the load is in air and completly immersed in water respectively then the lation n²/na is
Mukesh Reply
Properties of longitudinal waves
Sharoon Reply

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Source:  OpenStax, Siyavula textbooks: grade 10 physical science [caps]. OpenStax CNX. Sep 30, 2011 Download for free at http://cnx.org/content/col11305/1.7
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