Elements and Compounds

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So far this year, you have learned about the following:

  • An atom consists of positively charged protons and neutrons with no charge in a nucleus in the centre of the atom and much smaller electrons, which are negatively charged and on the outside of the atom.
  • Molecules are tiny particles made up of more than one atom. A water molecule is made up of two hydrogen atoms and one oxygen atom.
  • Elements are pure substances that are made up of one type of atom. There are 92 naturally occurring elements and some man-made elements.
  • Compounds are substances made up of more than one type of atom, tightly bound together. They can look and behave very differently to the elements that they are made up of.
  • Elements are organised in the periodic table according to the number of protons in their nucleus. Hydrogen is #1 because it has one proton, helium is number 2 because it has 2 protons etc.
  • Each column of the periodic table contains elements with characteristics in common – the noble gases in Group 8 are all very non-reactive elements for example.

Your assessment task for this unit of work is to produce an artefact that explains your understanding of the carbon cycle. It might be a poster, video, Voicethread, cartoon or slideshow. You could use Comic Life, ToonDoo, a common-craft style video or another tool. Make sure you include the following processes:

  • Photosynthesis – green plants use sunlight to convert carbon dioxide and water into carbohydrate (glucose) that is used by all other living organisms as the source of food.
  • Respiration – all living organisms (with the exception of a few bacteria) use oxygen to convert carbohydrates into energy, releasing carbon dioxide and water into the atmosphere.
  • Decomposition – Bacteria and fungi break down organic matter (leaves, wood, dead animals etc) into carbon dioxide and water during respiration.
  • Fossil Fuel formation – Oil, coal and gas are formed after millions of years under extreme pressure and high temperatures, from once living organisms such as trees and microscopic algae.
  • Combustion – wood, gas, oil, coal and other carbon-containing compounds can be burnt with oxygen to produce carbon dioxide.

Year 8 Science: Atoms and Molecules

Learning Intention: Students will be able to recognise the structure of atoms and molecules and understand some of the features of the periodic table. They will know that elements are pure substances made up of a single type of atom.

Success Criteria: You will be able to define atoms, molecules, elements and compounds. You will be able to draw a labelled diagram of an atom and explain why elements are arranged in the periodic table in rows and columns.

As you discovered this week, chemistry is everywhere! All substances are made up of atoms and molecules whether they be gases, liquids or solids. Some are pure substances (elements) made up of one type of atom, but most are compounds, made up of molecules of atoms of different kinds. We will complete several experiments next week, that show that a compound can be very different from the elements from which it is comprised. For example, hydrogen(H2)  and oxygen(O2) are colourless gases, but H20 (water) is a colourless liquid. Carbon (C) can be like charcoal, graphite or diamond, but carbon dioxide (CO2) is a colourless gas.

More information about atoms and elements at BBC Bitesize and the NDT Resource Centre.

Investigating Elements


Atom and hands machine drawingphoto © 2010 Bascom Oswald Hogue | more info (via: Wylio)








The drawing above is from Wylio,  a great place to search for free-to-use images for your blogs and wikis. It shows a diagram of the model of an atom, with a central nucleus and the path of three electrons around the outside. Elements are pure substances consisting of just one type of atom. Compounds are made up of molecules that consist of more than one type of atom. All the known elements are arranged in the periodic table in order of their atomic number.

elements_appDuring today’s lesson we will be looking at a range of different elements and describing them. You will use the Google doc, “Investigating Elements” to record your results. Click on the link and download the document onto your computer. There are 14 different elements to observe and complete each column – name, symbol, atomic number, description and what you might find that element in. We will also have some time this week to use the iPads to investigate “The Elements” app, which has amazing interactive images of each of the pure elements and extensive information about each element. This app can be purchased through the iTunes store for $13.99.