The 22nd element is Titanium. It has 22 electrons and is given the chemical symbol Ti. Titanium is a metal in the transition metal series. Like many other elements we have discussed it is not found as an element in nature. It is present in many minerals.
An interesting metal, it is light, strong and very unreactive. This means that it is useful in a variety of tasks. It is used in the space and aviation industry - a light strong metal. It is used by doctors to make replacement bones and joints. It is especially useful as a joint replacement as it isn't magnetic and this means that doctors can still use MRIs on the patient to investigate other complaints.
The most commonly found compound of Titanium is the white powder, Titanium Dioxide TiO2. This is a whiter than white" material which also has many uses.
It is used in paint, sun screen, toothpaste and even to put the white m&m writing onto m&m sweets!
At number 21 with 21 electrons and the chemical symbol Sc is Scandium. It is the first in the group known to chemists as Transition Metals. The transition metals are placed in the gap we left in the previous rows between the second and third columns. So why have chemists grouped these elements together and what is different about them. As you know be now, scientists like to group similar things together. It might be objects of the same colour, objects of the same texture, but for chemists it is materials with the same chemical behaviour. The alkali metals from group 1, Lithium, Soduim and Potassium for example, all have one electron in their outer shell and use this electron to bond with other elements. The common trait of the transition metals is that they don't fill all the spaces in the lower energy shells before putting electrons into higher energy shells and this means that they use electrons from more than one shell or energy level to combine with other elements. I suppose you could say that they have rules of their own, maybe they are the teenagers of the periodic table! Because of this transition metal elements give share or bond with different numbers of electrons in different situations.
So what of Scandium? Well it is a metal, present in relatively small amounts in the universe. It doesn't exist in its elemental form in nature so has to be extracted from minerals by scientists. This extraction is difficult and was only done successfully for the first time in 1937. It had been discovered many years before by a Scandinavian chemist, Lars Nilson. Prior to Nilson finding it, this element had been predicted by Mendeleev, the chemist who first put forward the idea that the elements could be organised in a table - the periodic table of elements.
It is light and strong and forms alloys with aluminium that are sometimes used in the planes and bicycles.
Scandium is one of the elements that hasn't been studied a great deal, however researchers continue to explore its characteristics and chemistry so perhaps in the future we will have more interesting uses for it.
Positioned next to Potassium and under Magnesium is Calcium. With the chemical symbol Ca and 20 electrons, Calcium is an element most children have heard about.
It is not naturally found in its elemental state - in other words you don't find lumps of calcium atoms on their own but when scientists remove the other elements leaving just Calcium they are left with a soft, grey / silver metal.
Calcium is grouped with Beryllium and Magnesium in the group known as the Alkali Earth Metals.
You may well have heard your parents encouraging you to drink milk, telling you that milk will give you strong teeth and bones. Milk is one of the foods that is rich in Calcium and Calcium is needed by the body. In fact our bodies are 5 per cent Calcium so for every 100g of our bodies 5 g are Calcium, and most of this Calcium is in our banes and teeth. It is the presence of Calcium in our bones that makes them opaque to x-rays. This characteristic is widely used to check to see if bones have been broken.
Calcium is also the fifth most abundant element in the earth's crust. Many rocks contain Calcium - limestone and chalk are both made from the Calcium containing compound Calcium Carbonate CaCO3. In caves, stalactites and stalagmites are Calcium containing compounds which have dissolved in water and moved through the rocks.
The mortar builders use to stick bricks together is a mixture of Calcium Hydroxide, known as lime, Sand and Water.
Cement is also made fromCalcium containing compounds.
Many Calcium containing compounds are not soluble in water but dissolve in other solvents such as acids. This means that buildings do not dissolve in rain but if you get acid rain which is caused by pollution then this acid rain can dissolve buildings. This can cause serious damage to old decorative buildings
Experiment of the Week Dissolving egg shells
You will need adult supervision 2 jam jars or jars with lids that seal Water Vinegar 2 eggs Hot water Basin containing cold water bottle with a large neck such as the one in this picture -
What to do Carefully place a raw egg into each of the 2 jam jars. Cover one with water and put on the lid. Cover the other with vinegar and put on the lid. After 24 hours remove the lids and carefully pour off the liquids. Compare the 2 eggs. The one which was in the vinegar should be soft - its shell dissolved in the vinegar. Fill the large necked bottle with hot water and then pour the water out. Sit the rubbery egg on top of the bottle. Cool the bottle by immersing it in the cold water. Your egg should be sucked into the bottle.
Potassium, with the chemical symbol K, is number 19. Last week we discussed Argon, the inert gas, with its outer electron shell full. This means that Potassium with one extra electron must have three full shells and only one electron in its outer shell. The symbol K comes from the Kalium - the Latin name for this material.
We have talked previously about how elements with the same number of electrons in their outer shells behave similarly chemically and scientists who noticed this started to group the elements according to this. They represented these groups in a now famous diagram known as the periodic table of elements. This week as well as talking about Potassium I am going to introduce you to this famous diagram. Each week we will add our new Element of the Week. It will be shaded in blue and have a red outline.
All the elements we have already discussed are included. Any that are gases at room temperature I have shaded in green. The metals are silver, the solids red and the metalloids purple.
So what about our element of the week, Potassium? Well, it is in the alkali metal group with Sodium and Lithium. Like Sodium, it is very reactive - just mad to give away its outer electron. Lumps of Potassium aren't found in nature because it has long since given away its outer electron to form a compound with some other electron hungry species. Scientists have prepared pieces of Potassium but to keep it you have to store it in oil. It burns in the air giving a purple coloured flame. Check out this video to see what happens http://www.youtube.com/watch?v=8HdAhs_-Y2g
Potassium containing compounds also give a purple flame when they are burned.
Although it is not found on its own, Potassium is very plentiful on the earth. It exists in many compounds. It is essential for both plant and animal like. Plants absorb Potassium salts from the earth and if you burn a plant you are left with a substance we call potash - the ash of Potassium! Farmers add Potassium fertilisers to their fields to help plant growth.
Potassium salts are also dissolved in the sea.
Potassium is essential for human life and each human body is 0.2% Potassium. To calculate how much Potassium your body contains take your weight in kg and multiply by 0.002. If you weigh 40 kg for example, 80g of that is Potassium! We get Potassium from fruit, nuts and vegetables with potatoes, bananas and dried apricots often being mentioned as good sources.
In our bodies we use Potassium to help our brains work properly, to help our muscles work well and to keep our fluid levels balanced.
People who are concerned about eating too much Sodium in their diets, but like their food to taste salty often use LoSalt. LoSalt is a mixture of Sodium Chloride (table salt) and Potassium Chloride.
Experiment of the Week: Work out how much potassium your body contains
You will need: Weighing scales Calculator or pen and paper
What you do: Weigh yourself. Multiply your weight by 0.002
The answer is the amount of your body that is Potassium!
Argon with the chemical symbol Ar is number 18. It is located on the periodic table in the third row of the right hand column underneath Helium and Neon. Like Helium and Neon, Argon is a member of the inert or noble gas family. This means that it is a gas at room temperature and that it is a very stable material that does not react with other elements, or itself for that matter.
Previously we have talked about the fact that air is a mixture of gases - mostly Nitrogen (78 parts of every 100) and oxygen (21 parts of every 100). Of the remaining 1 part a large amount of that is Argon.
At number 18, Argon has 2 electrons in its inner shell and 8 in each of the 2nd and 3rd shells. This means that all 3 electron shells are full. It is these full electron shells which make Argon so stable - it is neither looking for additional electrons to fill up the last few spaces nor looking to give away a few electrons to empty the outer shell.
The name Argon comes from the Greek word for lazy - very appropriate for an element which just won't react!
I was asked recently why the inner electron shell only has 2 electrons and the 2nd and 3rd 8. Well this is because in close to the nucleus the inner shell is very small and can only fit 2 electrons. The 2nd and 3rd shells are bigger and can fit 8 each. When we move on to the next row we will see that the 4th shell is considerably bigger and can fit an extra 10 electrons.
I was also asked about the position of the columns and the gaps in the first 3 rows. Well the elements are grouped in columns along with other elements with similar chemical behaviour. Helium behaves similarly to Neon and Argon so is placed in that group - it is in the group with full outer shells, not the group with 2 electrons in the outer shell.
So what is Argon used for? Well the main use is in situations when you want to prevent other reactions taking place so Argon is used for welding. It is also sometimes used as a preservative and also as a fire extinguisher.
Like Neon it becomes coloured when an electrical current is passed through it so it is used to make blue/purple advertising signs.
