Every card in The periodic table, Year 9
The whole deck, in order — so you can read it through before your child ever sees it.
- Going down Group 7, fluorine and chlorine are gases, bromine is a liquid and iodine is a solid. What state would you predict for astatine, the next element down? (one word)
Solid
HintFollow the direction the pattern is already moving in.
WhyAstatine is so rare and so radioactive that nobody has collected enough of it to look at. Chemists predict its state from the trend in its group, which is exactly what the periodic table is for.
- The melting points of the Group 1 metals fall as you go down the group: lithium 181 °C, sodium 98 °C, potassium 63 °C. Would you expect rubidium, the next one down, to melt above or below 63 °C?
Below
HintEach step down the group has moved the number the same way so far.
WhyRubidium melts at about 39 °C, so it would turn liquid on a very hot day. A steady trend through three elements gives a prediction you can trust; the more elements that fit a pattern, the more confidence it deserves.
- In Group 7, chlorine is more reactive than bromine, and bromine is more reactive than iodine. Is astatine, below iodine, likely to be more or less reactive than iodine?
Less reactive
HintThis group runs the opposite way to the alkali metals.
WhyEvery group has its own trends. In Group 1 the metals get more reactive going down; in Group 7 the non-metals get less reactive going down. You have to know the direction for each group before you can predict with it.
- Elements in the same ____, or vertical column, of the periodic table have similar chemical properties, which is what lets chemists predict how an unfamiliar element will behave.
group
HintLithium, sodium and potassium share one; so do the halogens.
WhyLithium, sodium and potassium all fizz in water and all form alkalis, because they share a column. Elements side by side in a row can be as different as a metal and a gas.
- In what order did Mendeleev arrange the elements in his periodic table of 1869?
In order of atomic weight
HintHe used the one number that chemists of his day could measure for each element's atoms.
WhyAtomic weight, now called relative atomic mass, says how heavy an element's atoms are compared with others. When Mendeleev listed the elements from lightest to heaviest, similar ones turned up at regular intervals.
- Mendeleev left a gap below silicon and predicted the properties of the missing element. Which element, discovered in 1886 and named after its discoverer's country, filled the gap? (one word)
Germanium
HintThe country is in central Europe, and its Latin name begins with G.
WhyMendeleev predicted its atomic weight, its density and the formula of its oxide fifteen years before it was found. The match was so close that few chemists doubted his table afterwards.
- Gallium was discovered six years after Mendeleev's table appeared, with properties close to those he had predicted for it. Why did this persuade chemists that his table was right?
It had correctly predicted something nobody yet knew
HintCompare explaining facts already in hand with forecasting a fact still to be found.
WhyAny tidy arrangement can be made to fit the facts already known. A scientific idea earns real trust when it risks a prediction that could have turned out wrong, and the prediction then comes true.
- Where the order of atomic weights would have put an element in the wrong family, Mendeleev swapped the order, so that elements with similar ____ stayed in the same column.
properties
HintThink of how an element looks, behaves and reacts.
WhyTellurium is slightly heavier than iodine, but iodine plainly belongs with chlorine and bromine, so he placed tellurium first. He trusted the pattern of behaviour over the weights, and later discoveries showed he was right to.
- Are most of the elements in the periodic table metals or non-metals?
Metals
HintPicture how much of the table lies to the left of the staircase line.
WhyAbout three-quarters of the elements are metals. The non-metals are squeezed into the top right-hand corner, even though they include most of the elements that make up the air and living things.
- Magnesium is near the left-hand end of Period 3 and sulfur is near the right-hand end. From their positions alone, which of the two would you expect to conduct electricity?
Magnesium
HintDecide which side of the staircase line each one falls on.
WhyElements on the left of a period are metals, and metals conduct electricity. Sulfur lies to the right of the dividing line, so it is a non-metal: a brittle yellow solid that does not conduct.
- Which element sits on the dividing line between the metals and the non-metals in Period 3, with aluminium on one side of it and phosphorus on the other? (one word)
Silicon
HintIt is used to make computer chips, and a famous valley in California is named after it.
WhyElements on the line are hard to classify. This one is shiny like a metal but brittle like a non-metal, and it conducts electricity only a little, which is exactly what makes it useful in electronics.
- Sulfur is a non-metal. When it burns it forms an oxide that dissolves in water. Is the solution acidic or alkaline?
Acidic
HintThink what coal smoke containing this oxide does to rainwater.
WhyThe oxides of non-metals are acidic, while the oxides of metals are bases. So the change across a period, from metal to non-metal, shows up in the chemistry of the oxides as well as in how the elements look.
1★ KS3-CHEM-PER-0013
2★ KS3-CHEM-PER-0014
3★ KS3-CHEM-PER-0015
4★ KS3-CHEM-PER-0016
5★ KS3-CHEM-PER-0017
6★ KS3-CHEM-PER-0018
7★ KS3-CHEM-PER-0019
8★ KS3-CHEM-PER-0020
9★ KS3-CHEM-PER-0021
10★ KS3-CHEM-PER-0022
11★ KS3-CHEM-PER-0023
12★ KS3-CHEM-PER-0024
Keep what you learn
Here, nothing is saved. In your child’s own sky every card is scheduled — it comes back just before they’d forget it — and the professor who wrote it is one tap away.