Learning Objective

In this lesson we will revise the classification of matter and atomic structure.

Learning Outcomes

By the end of this lesson you will be able to:

  • Distinguish between pure substances and mixtures.
  • Distinguish between elements and compounds.
  • Describe the arrangement of atoms in pure substances.
  • Describe the subatomic structure of atoms, including protons, neutrons and electrons.
  • Define atomic number and mass number, and explain what isotopes are.
  • Describe the configuration of electrons for the first 20 elements.

 
atoms elements and compounds

(Image: vchalup, Adobe Stock)

Lesson Topics

1 | Pure Substances and Mixtures

2 | Elements and Compounds

3 | Atoms, Molecules and Lattices

4 | Structure of Atoms

5 | Electron Configuration

 


Lesson Summary

  • A chemical subunit is the smallest building block of a pure substance that is unique to that substance.
  • Atoms are the simplest type of chemical subunit.
  • Atoms can exist individually or connected to other atoms by chemical bonds.
  • Molecules are discrete arrangements of atoms joined by chemical bonds.
  • Lattices are networks of atoms joined by chemical bonds.
  • Pure substances are made up of one type of chemical subunit.
  • They have defined physical and chemical properties.
  • Elements are pure substances made up of one type of atom.
  • These atoms may exist individually, or as molecules or lattices.
  • Elements cannot be broken down into simpler substances.
  • Compounds are pure substances made up of two or more different types of atoms.
  • These structures may be molecules or lattices.
  • Compounds can be broken down (chemically) into simpler substances.
  • Atoms are made up of three main subatomic particles – protons, neutrons and electrons.
  • Protons and neutrons form a cluster at the centre of the atom, called the nucleus.
  • Electrons orbit the nucleus, in electron shells, forming an electron cloud.
  • Protons have a mass of 1 atomic mass unit and a positive charge (+1).
  • Neutrons have a mass of 1 atomic mass unit and no charge.
  • Electrons have a mass of 1/1840 of an atomic mass unit and a negative charge (–1).
  • Atoms that have the same number of protons but a different number of neutrons are called isotopes.
  • The atomic number of an atom is equal to the number of protons in the atom.
  • It determines the type of atom.
  • The mass number of an atom is equal to the total number of protons and neutrons in the atom.
  • This is the number of particles in the nucleus, which largely determines the mass of an atom.
  • Electron configuration describes the arrangement of electrons in shells around the nucleus of an atom.
  • A maximum of 2 electrons can occupy the first shell.
  • A maximum of 8 electrons can occupy the second shell.
  • A maximum of 18 electrons can occupy the third shell, but the fourth shell will begin to fill once the third shell contains 8 electrons.
  • A maximum of 8 electrons can occupy the valence shell (outermost shell).

 
molecules

(Image: MasterTux, Pixabay)

(Header image: geralt, Pixabay)

 


 
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Year 10 Chemistry Print Workbook Australian Curriculum

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