Atoms, elements and the Periodic Table
The structure of an atom, the Periodic Table, symbols, and metals, non-metals and semi-metals. Read one part at a time and tap “I know this”. Then test yourself in the quiz.
Know it already? Jump straight to the quiz
The atom
The atom is the smallest particle of an element. Carbon dioxide is a compound; only a mixture can be separated physically.
The Periodic Table
| Symbol | Element | Kind |
|---|---|---|
| H | Hydrogen (first element) | Non-metal |
| He | Helium | Non-metal (noble gas) |
| C | Carbon | Non-metal |
| O | Oxygen | Non-metal |
| Na | Sodium | Metal |
| Si | Silicon | Semi-metal |
| S | Sulfur | Non-metal |
| K | Potassium | Metal |
| Ca | Calcium | Metal |
Scientists use symbols, because symbols are the same in every language.
Metals and non-metals
Most metals are shiny, conduct heat and electricity well, are malleable (can be hammered into shape) and ductile, and have high melting points. Most non-metals are dull, brittle when solid, and poor conductors (insulators); they can be solids, liquids or gases. A semi-metal has some properties of both. Silicon is used in computer chips and solar panels.
Mendeleev and the first 20 elements
Dmitri Mendeleev arranged the elements in a table according to their properties in the 1860s. Metals stand on the left, non-metals on the right, and semi-metals in a zig-zag strip between them. Hydrogen is the exception: it is a non-metal (a gas), but it sits at the top left. Mercury is the only metal that is liquid at room temperature.
| Symbol | Element | Kind |
|---|---|---|
| H | hydrogen | non-metal |
| He | helium | non-metal |
| Li | lithium | metal |
| Be | beryllium | metal |
| B | boron | semi-metal |
| C | carbon | non-metal |
| N | nitrogen | non-metal |
| O | oxygen | non-metal |
| F | fluorine | non-metal |
| Ne | neon | non-metal |
| Na | sodium | metal |
| Mg | magnesium | metal |
| Al | aluminium | metal |
| Si | silicon | semi-metal |
| P | phosphorus | non-metal |
| S | sulfur | non-metal |
| Cl | chlorine | non-metal |
| Ar | argon | non-metal |
| K | potassium | metal |
| Ca | calcium | metal |
Remember this and test yourself
- The atom’s nucleus has protons (+) and neutrons (no charge); electrons (−) move around it.
- There are about 118 known elements, all in the Periodic Table.
- A group is a column (similar properties); a period is a row.
- Symbols: H hydrogen (the first), He helium, C carbon, O oxygen, Na sodium, K potassium.
- Metals are shiny and conduct heat and electricity; non-metals are mostly dull and poor conductors; semi-metals such as silicon (computer chips) are in between.
Write these points in your book. Read them again the night before the test.
Proton = Positive. Neutron = Neutral. Electron = the fast negative one running around outside.
Important words
First say what the word means, then turn the card over.
Match column A to column B
Tap a word in column A, then its meaning in column B. You can also start in column B.
True or false?
Read the question and the answer. Is the answer right? Tap True or False.
Now the real quiz!
The quiz has many more questions on this topic. Every question shows straight away whether you are right and explains why.
Take the quiz: Atoms, elements and the Periodic Table- Read one part together and ask your child to tell it back in their own words.
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Follows CAPS for Grade 7 Natural Sciences. Always check your teacher’s notes and textbook too.