Yttrium

Yttrium


The 39th element in the series is Yttrium. Yttrium is a transition metal. The transition metals sit in a block in the centre of the table. Yttrium appears in the first position of the second row. This tells us that it has 1 electron in its outer d-orbital.

Although it is never found in nature as a free element, when isolated it is a slivery metal. The surface layer reacts with oxygen giving a passivating layer so Yttrium is stable in air.
It has no role in biology and is thought to cause lung problems in humans.
It was discovered in the late 1700s near Yetterby in Sweeden hence the name -Yttrium.


Yttrium has some interesting uses. As it is very hard, a Yttrium aluminium compound is used to simulate diamond gemstones. Yttrium is also used to start the reaction in which ethene is polymerised to make polythene. When something is used to start a reaction but not used up in the reaction itself scientists call this material a catalyst so we would say that Yttrium catalyses the ethene polymerisation. 

From Hydrogen to Tellurium - Strontium

Strontium 


Strontium is number 38 and has the chemical symbol Sr. In the same group as Magnesium and Calcium, Strontium is one of the Alkali Earth Metals. Strontium is very reactive with both water and air and therefore doesn't exist naturally in its elemental form. When isolated the metal is a silvery grey colour, however it reacts in air to give a yellowish coloured compound.


It was discovered in Scotland and it is named after the village - Strontian where it was discovered.


Students come across Strontium in their studies because when burned its salts give a characteristic red colour. This characteristic or trait also mean that it is commonly used in fireworks to give a red colour.


Below are links to a couple of video clips showing strontium salts burning with their characteristic red flame.
http://www.youtube.com/watch?v=vltFchuGi0Y


http://www.youtube.com/watch?v=BGd-bCpLDvE&feature=related

From Hydrogen to Tellurium - Rubidium

Rubidium


For the 37th element, we jump back to the left hand side of the periodic table. Rubidium, with the chemical symbol Rb, is an Alkali Metal in the same group as Hydrogen, Lithium, Sodium and Potassium. What you. Should remember about these elements is that each of them have only one electron in their outer shell making them very reactive. In fact, rubidium is the most reactive we have met so far. The increase in reactivity is due to the distance of the outer electrons from the nucleus - the further away the electron is from the nucleus the less tightly the atom can hold onto the electron. Rubidium is very reactive in air and burns spontaneously in water.


Rubidium is a metal, solid at room temperature, but with a melting point of 40 degrees centigrade.


Rubidium is the 23rd most common element in the earth's crust. It is also present dissolved in sea water.

From Hydrogen to Tellurium - KRYPTON

Krypton 


Krypton is the chemical element with the atomic number 36 and the chemical symbol Kr. In the periodic table it is positioned at the end or right hand side of the fourth row, underneath Helium, Neon and Argon. This tells us that it has the right amount of electrons to fill its outer electron shell. We have already learned that elements with full outer electron shells are not reactive and Krypton is no exception. It is the next member of the inert gas family.

Maybe you knew Krypton was an element, maybe you didn't. It is a colourless, odourless, tasteless gas. It is found in very small amounts in the atmosphere. Neon and Argon are well knows for their ability to produce coloured light, red and blue respectively when an electrical current is passed through them. Krypton also has this property or trait but the light it produces is very bright white light.


Interestingly, Krypton has been used in defining the length of a meter. According to www.surveyhistory.org The French originated the meter in the 1790s as one/ten-millionth of the distance from the equator to the north pole along a meridian through Paris.  It is realistically represented by the distance between two marks on an iron bar kept in Paris.  The International Bureau of Weights and Measures, created in 1875, upgraded the bar to one made of 90 percent platinum/10 percent iridium alloy.

In 1960 the meter was redefined as 1,650,763.73 wavelengths of orange-red light, in a vacuum, produced by burning the element krypton (Kr-86).  More recently (1984), the Geneva Conference on Weights and Measures has defined the meter as the distance light travels, in a vacuum, in 1/299,792,458 seconds with time measured by a cesium-133 atomic clock which emits pulses of radiation at very rapid, regular intervals.

None of the definitions changed the length of the meter, but merely allowed this length to be duplicated more precisely.

Fans of Superman will know that Krypton is a fictional planet, the native home of Superman. The story goes that the planet exploded, everyone was killed, except Superman, who was shot out from the exploding planet and ended up on earth.

Experiment of the week

Super strong paper

Given that Superman is so strong, it seems fitting to investigate the strength of paper this week.

You will need:

3 A4 sheets of 80g/m2 paper

3 empty spreadable butter containers or similar

a ruler

sand or small weights to load weight onto your bridge

a spoon

adult supervision

What to do

Position 2 of the butter containers 15 cm apart

Use the 3 sheets of paper to bridge the gap

Put the third empty container onto your bridge and slowly fill it with sand.

How much sand can you load onto the bridge before it collapses?

Who can make the strongest bridge?

Post your results and photos below