Download Structure of the atom

topic: Elements, compounds and mixtures
activity: Structure of the atom
Students discover the major sub-atomic particles and learn about the electron configurations of the first 20
elements.
Suggested time: 35 minutes
Summary of Key Learning Points
Students:
- discover the three main sub-atomic particles and their characteristics
- find out how to represent particular atoms using nuclide symbol notation
- understand how many electrons can fit in the first few electron shells
- observe the electron configurations of the first 20 elements
- write the electron configurations for the first 18 elements
Structure of the atom
5 minutes
The first page features a neon-20 atom. The nucleus is a 3D object that can be 'grabbed' and rotated. Have
students start by counting the number of protons (red) and the number of neutrons (blue). They can then
confirm their count using the 'explore' buttons. The main properties of each sub-atomic particle are given.
Emphasise that the electrons are much smaller than the protons and neutrons.
How to represent atoms
5 minutes
This page shows how to represent atoms using nuclide symbol notation. It should also be emphasized that
the number of electrons will only equal the number of protons in a neutral atom. Ions will obviously have
unequal numbers of protons and electrons.
Class activity: Have students work out how many protons, neutrons and electrons each of neon’s isotopes
has. Also have them write the nuclide symbols for carbon’s isotopes, carbon-12, carbon-13 and carbon-14.
Challenge
10 minutes
Students look at several nuclide symbols and write the appropriate numbers in the data card.
Answers:
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topic: Elements, compounds and mixtures
activity: Structure of the atom
Calcium-40: mass number = 40; atomic number = 20; number of protons = 20; number of neutrons = 20;
number of electrons = 20 (Inquiry point 1)
Carbon-14: mass number = 14; atomic number = 6; number of protons = 6; number of neutrons = 8; number
of electrons = 6 (Inquiry point 2)
Nitrogen-14: mass number = 14; atomic number = 7; number of protons = 7; number of neutrons = 7;
number of electrons = 7 (Inquiry point 3)
Krypton-85: mass number = 85; atomic number = 36; number of protons = 36; number of neutrons = 49;
number of electrons = 36 (Inquiry point 4)
Potassium-39: mass number = 39; atomic number = 19; number of protons = 19; number of neutrons = 20;
number of electrons = 19 (Inquiry point 5)
Adding electrons
5 minutes
Students use the slider to view the first 20 elements with their election configurations. Tell them that the
maximum number of electrons in any shell = 2 x (shell number)2. This means that the third shell fits 18
electrons, but it is stable with 8. Due to sub-shell filling order, two electrons go into the 4s shell before the 3d
orbitals fill. This is why the electron configuration of potassium is 2, 8, 8, 1 not 2, 8, 9, and calcium’s is 2, 8,
8, 2 not 2, 8, 10.
Electron configurations
10 minutes
By selecting each element in turn, students can write the electron configuration of the first 18 elements.
Answers:
Hydrogen = 1
Helium = 2
Lithium = 2, 1
Beryllium = 2, 2
Boron = 2, 3
Carbon = 2, 4
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topic: Elements, compounds and mixtures
activity: Structure of the atom
Nitrogen = 2, 5
Oxygen = 2, 6
Fluorine = 2, 7
Neon = 2, 8
Sodium = 2, 8, 1
Magnesium = 2, 8, 2
Aluminium = 2, 8, 3
Silicon = 2, 8, 4
Phosphorus = 2, 8, 5
Sulfur = 2, 8, 6
Chlorine = 2, 8, 7
Argon = 2, 8, 8 (Inquiry point 6)
Suggested completion levels
Basic – Inquiry point goal = 2
Students at this level will: identify the three main sub-atomic particles; recognise what the numbers in a
nuclide symbol mean; write the electron configurations for the first 10 elements.
Core – Inquiry point goal = 4
Students at this level will: describe the three main sub-atomic particles and their characteristics; understand
nuclide symbols; write nuclide symbols for given isotopes; write the electron configurations of the first 18
elements.
Advanced – Inquiry point goal = 6
Students at this level will: describe the three main sub-atomic particles and their characteristics; understand
nuclide symbols; write nuclide symbols for given isotopes; write the electron configurations of the first 20
elements; explain the unexpected electron configurations for potassium and calcium.
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