From Hydrogen to Tellurium - BROMINE

Bromine


At number 35 is Bromine with the chemical symbol Br. Another non-metal, Bromine is the first element we have come across that is a liquid at room temperature. It is a red/brown liquid and when heated it boils to produce a red/brown gas at 60°C.

Bromine is in the same group as fluorine and chlorine and is therefore a halogen. Halogens are very reactive, they have space for one more electron in their outer electron shell and are very keen to fill that space by taking an electron from anything that will give them one. In terms of reactivity Bromine is less reactive than fluorine or chlorine but more reactive than iodine which in in the row below it in the table.


Bromine gas has a horrible smell. It is suffocating so not a good idea to have it around. Bromine liquid is corrosive to human tissue. The name Bromine comes from the Greek word Bromos which means stench.


Bromine is extracted from natural brine deposits taken from salt springs.


It is used as a dye, in pesticides and as a flame retardant in plastics.

From Hydrogen to Tellurium - SELENIUM

Selenium


Selenium is the 34th element, a nonmetal, it has 2 allotropes - a purple/gray one and a red one, the purple/gray one being the most stable. Its chemical symbol is Se.

It is rarely found in nature but occurs as a compound in minerals.


The purple/gray allotrope is a semi conductor and it has an unusual property - it is a better conductor in the light than in the dark.


At number 34, Selenium has 34 electrons. This means that it has 2 spaces in its outer shell - just like oxygen and sulphur. Selenium forms similar compounds to sulphur - SeO2 and H2Se for example


Although it is extremely toxic in large doses, it is present at trace levels in humans and thought to be essential for the correct functioning of the body. We get our Selenium from eating plants and animals that contain Selenium. Brazil nuts have the highest concentration of any food. It is also contained in crab and lobster meat.

From Hydrogen to Tellurium - ARSENIC

Arsenic

The 33rd element is Arsenic. This element I associate with all sorts of sinister things - murders, poisonings, mystery and intrigue. In Agatha Christie novels it was one of the main causes of death in her victims.
Toxic chemicals are labelled by scientists with the scull and crossbones  to warn users to be especially careful with them, though it is recommended that chemists treat all chemicals as if they might be toxic to prevent any unwelcome surprises.


In terms of its properties or traits, Arsenic is a metalloid or semi metal, sitting in the periodic table between the metals and the non-metals. Arsenic occurs in a range of minerals as well as in its elemental form. In its elemental form it is usually a gray crystalline solid but like carbon and phosphorus, it has other allotropes. When heated it goes straight from a solid to a gas - we call this subliming.
Arsenic forms compounds with many other elements - oxygen, sulphur, etc
In the past arsenic compounds have been used as insesticides, weedkillers and wood preservatives. Thanks to the Elements exhibition in the Science Gallery I also learned that Arsenic compounds were also used by interior designers to give a green colour to wall papers.
A modern day use for Arsenic is in the computer industry where it is used for its semiconductor abilities.

From Hydrogen to Tellurium - GERMANIUM

Germanium


Germanium, with 32 electrons, is the 32nd element in the table. During the week I came across this very colourful periodic table and have included it because it shows the different chemical groups in different colours. As you can see, Germanium is one of the semi metals often called metaloids. It is one that prior to this week I knew very little about.

Named after the country, Germany, Germanium was discovered in 1886 by a German chemist. It is obtained today by smelting zinc ores and from the burning of certain types of coal. It is the fifteenth most abundant element in the earth's crust.


Its main use is in the computer industry where it is used in semi conductors.


Interestingly, Germanium has a low toxicity in mammals but is highly toxic to some bacteria. Investigations are going on into its use as a means of killing bacteria or treating bacterial infections.


In some factories Germanium dioxide is used to help start the reaction used in the making of PET for drinks bottles.

From Hydrogen to Tellurium - GALLIUM

Gallium


The 31st element, Gallium is an unusual material. It is not found in nature but can be extracted from minerals. 

Gallium, which comes under Aluminium in the periodic table, is a metal. Most metals have high melting points but there are a few exceptions and Gallium is one of those exceptions. You might already know that Mercury, another metal, is liquid at room temperature. Gallium is normally solid at room temperature but it melts at 29 degrees centigrade. This means that its melting point is similar to that of chocolate and any of you who eat chocolate and especially those of you who came to Anyone 4 Science summer camps this year will know that you can melt chocolate in your hand. Well it is exactly the same for Gallium - hold a piece in your hand, which is at 37 degrees centigrade and it will melt! Fairly cool don't you think. 


Because aluminium and Gallium look similar a chemistry trick is to make a teaspoon out or gallium instead of aluminium and offer this to your victim to stir their coffee, tea or hot chocolate. Guess what happens to their spoon? - It melts and goes to the bottom of the cup. Check out this disappearing spoon video - http://www.youtube.com/watch?v=QaJ_Yxj9bG8


Gallium also has a big range between its melting and its boiling temperature. This means it is suitable to use in a thermometer.

Another interesting property of Gallium is that is expands as it solidifies. It is unusual for this to happen as most materials contract as they cool. Another exception to this contracting as it cools rule is water. As water freezes it also expands. It is this property that causes pipes to burst when water freezes. If you stored Gallium in a glass container it would crack the container as it cooled.


Check out this cool video made by scientists at Nottingham University showing how to make Gallium beat like a heart. http://www.youtube.com/watch?v=N6ccRvKKwZQ&feature=player_embedded




Experiments of the Week


To show that water expands as it freezes


You will need:
Empty 500 ml PET bottle
water
measuring cylinder
marker


What to do:
Measure 400 mls water into the measuring cylinder and transfer it into the 500ml bottle.
Mark the line showing where the water comes to in the bottle.
Put the bottle of water in the freezer and leave overnight.
Take the bottle our of the freezer and mark the new level of the ice in the bottle.
Allow the liquid to melt. 
Fill the bottle to the new mark.
Pour all the water into the measuring cylinder.
Calculate by how much the ice expands.




Experiment 2


Make your own Thermometer


You will need:
Glass bottle.
Water
Food colour
Drinking Straw
modelling clay / blu tack
cold water
basin with hot water



What to do:
Colour some cold water with a few drops of food dye.
Fill the glass bottle with coloured cold water. 
Using the modeling clay fix the straw so that it is sealed into but sticking out of the bottle.
Stand the bottle in the basin of hot water


What happens? Leave your comments below.

From Hydrogen to Tellurium - Zinc

Zinc


The last element in the first row of transition metals is Zinc. With an atomic number of 30, Zinc has 30 electrons. This means that Zinc has a full 4S orbital and also a full 3D orbital, but empty 4P orbitals and as a result of this Zinc is quite reactive and has lots of chemical similarities to Magnesium.


Zinc is a metal, not found in the elemental state but normally found in nature as Zinc Sulphide. Zinc metal is extracted from this mineral. We know that humans have known about Zinc for a long time because Zinc is combined with copper to give bronze which was used extensively in the bronze age. The Bronze age started about 3300BC and continued until 1200BC.


Zinc is a bluish white metal with a melting point of 419 degrees centigrade. Although this is very hot, it is much lower than the metals we have been considering over the last few weeks. The surface of the metal reacts quickly with air but the layer of oxide that is formed is unreactive and makes a layer which is difficult to penetrate.


This unreactive surface layer is widely used to help prevent oxidation of other metals. To prevent steel oxidising it is covered with a thin layer of Zinc. Zinc forms a tough exterior layer and prevents the steel from rusting.


Zinc is also used in batteries.


Zinc is an essential trace element for humans, plants and animals. We get zinc in our diets from red meats, beans, some nuts and seeds. 


Other interesting facts about Zinc compounds include the following
It is used in sunscreens to prevent sun burn
It helps to prevent nappy rash in babies
It is used in toothpaste to prevent bad breath
It is used to kill germs - particularly bacteria and fungi




Experiment of the Week
Make your own battery


You will need:
a copper coin
a zinc nail
tissue paper
salt water
a volt meter or a 3V buzzer


What to do:
dip the tissue paper into the salt water
Make a sandwich - copper, soaked tissue, zinc
either connect the voltmeter to the 2 metals and record the voltage or complete the circuit using the buzzer with the red wire attached to the copper and the black wire attached to the zinc.


Post your results in the comments section below.

From Hydrogen to Tellurium - COPPER

Copper

The 29th element is a well known element - Copper. Another metal, most children will be able to tell you that 1, 2 and 5 cent Euro coins are Copper.

This metal is a pinkish brown colour. When polished it is shiny but it reacts with air to give a dull oxide. We also associate a green colour with Copper. If you wear a Copper bracelet your will get a green deposit on it. Some churches have copper decorating their roofs. This Copper started out life as a shiny metal but over time, reacting with the air and pollutants in the air it has become green.

This is a photo of the church in Rathmines on the south side of Dublin. The green roof is made from Copper.

Copper has 29 electrons. They fill up the orbitals as follows: 1S 2, 2S 2, 2P 6, 3S 2, 3P 6, 4S 1, 3D 10. This means that the 3D orbital is full as a D orbital can fit 10 electrons. This is the first element we come across to have a full D orbital.

Copper is a good conductor of heat and of electricity. It is used in wires for carrying electricity.

Copper is also used in many of our homes for the plumbing. The copper pipes carry the water around the house. Where we live the water is slightly acidic as it comes through granite to get to our well. I can see the effects of this in our bathroom and in our hair. THe slightly acidic water travelling through the Copper pipes reacts with and dissolves some of the Copper. I see this as a green deposit in our shower tray and basins. It also shows up in the hair of blond family members - wash your blond hair in this Copper containing water and after a while your hair will have a green hue. This is especially visible on sunny days when the sun shines on the hair. What is causing the hair to appear green? The Copper from the pipes chelates or bonds to the hair.

Can you melt Copper? The answer is yes, but not in the flame of a candle which just doesn't get hot enough. Copper melts at 1084 degrees centigrade.

Copper isn't magnetic but an interesting experiment to do is to test the 1, 2 and 5 cent Euro coins to see if they are magnetic. What did you find? Can you explain this?

Experiment of the Week

Take Copper from a coin and deposit it on a nail.

You will need:

small cup or beaker

salt

vinegar

about 10 copper coins - dirty ones are fine

kitchen roll

nail

What to do:

Half fill a small beaker with vinegar (use approx 20 - 30 mls)

Add a teaspoon of salt.

Put your coins into the salt vinegar mix and leave for about 30 minutes.

Remove the coins and leave to dry on a piece of kitchen roll. Do not discard the liquid as you will need it for the next part of the experiment.

Dip a nail into the salt vinegar mixture and leave for about 10 minutes.

Remove the nail and examine it carefully.

What has happened?

Return to the coins. What has happened to them?

Explain your observations.

Leave your comments below.

From Hydrogen to Tellurium - NICKEL

Nickel


Element 28 is Nickel which is another metal from the transition metal series. The name Nickel is familiar to many people, not because they know it as another element but because of the slang name given to the US 5 cent coin.

Although known as a Nickel, the 5 cent in fact is made of a mixture of 75% copper and 25% nickel. In spite of this it has the silvery colour of Nickel.

Like Iron and Cobalt, Nickel is magnetic, however the US Nickel is not magnetic as it doesn't contain enough Nickel to make it magnetic.


Nickel is used in stainless steel iron with 18% chromium and 8% Nickel.


Much "good" cutlery though referred to as silver isn't actually silver but nickel silver. Nickel silver is an alloy of copper, nickel and zinc. This same alloy is also used for making musical instruments and costume jewellery.

      

At the summer camps this year we have been looking at melting points. We found that sugar would melt at 186 degrees centigrade. Nickel also melts but at the much hotter temperature of 1455 degrees centigrade.