Mendeleev and the development of the Periodic table

Over time as elements have been discovered scientists have tried to observe patterns in their properties and behaviours, looking to list and categorise them accordingly. 

Döbereiner spotted patterns in sets of 3 elements, he called them triads. Newland arranged elements in order of atomic mass, he found that every 8th element had similar properties (although this did not work exclusively for all elements).  It was Dmitri Mendeleev who really got to grips with categorising elements into a table.  His ideas eventually led to the modern Periodic Table that we have now.   The video below explains the development of the Periodic Table:

So Mendeleev arranged his table in the following way:

• elements were arranged in rows of increasing atomic mass and columns of elements with similar properties,
• gaps were left for yet undiscovered elements, Mendeleev even predicted the atomic masses and properties of these elements. (Once discovered, it was found that he was very accurate with his predictions),
• where elements were in the wrong place when sorted by atomic mass, he swapped then so that they would be grouped by their properties e.g. tellurium and iodine were swapped so that iodine would be grouped with fluorine, chlorine and bromine,
• some elements were paired in the same space.

Mendeleev's table did not include a transition metal block or the Noble gases. As more was discovered about the atom and new elements found the Mendeleev's table evolved into the modern table that we now know.  In recognition of his role the 101st element was named after him - Mendelevium!

Reducing Our Impact on Global Warming - Carbon Capture and Storage

Evidence for the impact of carbon dioxide on global warming

There is much debate about the causes of global warming, some argue that it is just part of the Earths' natural cycle and that there have been periods of extreme heat and ice ages throughout the millennia. Whilst others say that increasing carbon dioxide in our time is contributing directly to global warming.  There are plenty of websites on the internet giving argue for and against these theories.  The Houston Chronicle blog typifies this showing that data can be used to argue for and against the impact of carbon dioxide. Click here.

The graph below (from http://www.discoveringantarctica.org.uk/alevel_2_3.html) shows a link between carbon dioxide levels and temperature over the last 600,000 years.  This data has been gathered by looking at ice core samples from Antarctica.  Click on the graph for more information.

It suggests that there is a link between carbon dioxide and temperature levels.  The greater the carbon dioxide the greater the temperature.  It also suggests that these temperature changes are cyclic.  At present the levels of carbon dioxide in our atmosphere are greater than at any time during the period of the graph above, it is also thought in some areas that the rise in global temperature is probably greater than would be expected in these normal temperature cycles.

The Artic Climate Impact Assessment (website click here) has shown that since the onset of the Industrial Revolution (1800s onwards) where the use of fossil fuels has increased, carbon dioxide emissions have increased rapidly as has global temperature.

Carbon-dioxide levels in the air closely track temperature records for the past 10 centuries. If they continue to parallel each other, global warming will only get worse. From: http://whyfiles.org/211warm_arctic/ Courtesy Arctic Climate Impact Assessment

How can carbon dioxide emissions be reduced?

Scientists believe that reducing carbon dioxide emissions could help reduce levels of global warming.  One method of doing this is by carbon capture and storage, the video below explains how this is being undertaken in Australia by the Australian Coal Association:

To summarise:

• carbon dioxide can be captured at the point of production,
• condensed into liquid form,
• then stored deep under sea beds in geological formation such as old oil fields, or underground in geological rock formations such as old coal seams.

For more information visit the Carbon Capture & Storage Association website. Click here.

Global Warming

What is Global Warming?

Carbon dioxide is one of a number of gases in our atmosphere that are known as 'greenhouse gases'.  The sun’s rays (made up of UV and Infra-red (IR) rays) pass through the atmosphere and warm the surface of the Earth.  These rays are reflected out into space again. Greenhouse gases such as carbon dioxide absorb some IR rays from the sun, and reflect them back towards the Earth, warming up the atmosphere and the Earth's surface.  These gases are needed as without them the surface temperature would be approximately 33^oC colder than it is now making it highly unlikely that plant and animal life would survive.

The Carbon Cycle

 

The carbon cycle is a naturally occurring process where carbon dioxide is removed from the atmosphere by organisms (such as plants) undergoing photosynthesis:

 

 

carbon dioxide  +    water     ---------->    glucose            +   oxygen

6CO₂(g)       +    6H₂O(l)   ---------->    C₆H₁₂O₆(s)         +   6O₂(g)

The carbon is trapped in the plant as glucose, this carbon can be transferred to animals when plants are eaten.

 Both plants and animals use glucose as a source of energy in the process of respiration:

glucose        +     oxygen  ---------->    carbon dioxide      +   water

C₆H₁₂O₆(s)    +     6O₂(g)    ---------->    6CO₂(g)                  +   6H₂O(l)

This (along with decomposition of plants and animals when they die) releases carbon dioxide back into the atmosphere.  This is not a problem as the amount carbon dioxide released is the same as the amount taken in when the plants grew originally, so the process can be considered ‘carbon neutral’.

 

On this basis carbon dioxide levels in the atmosphere would be sufficient to maintain a temperate climate.

Why is Global Warming an issue?

The problem exists in the combustion (burning) of fossil fuels.  Fossil Fuels contain carbon that was trapped millions of years ago.  This releases extra carbon dioxide into the atmosphere, which is not part of the natural carbon cycle.

 

This carbon dioxide absorbs more IR rays from the sun reflecting them back towards the Earth's surface, increasing the surface temperature.  This process is known as global warming, the video below describes the process:

 

 

Issues with Global Warming

As the surface temperature of the Earth increases a number of problems occur, many of which are linked together:

• Polar ice caps melt more quickly – sea levels rise, causing flooding in low lying coastal areas. Destroying habitats in both of these regions.

• Climate changes – Temperature rises will cause increased rainfall in some areas, tropical storms and flooding, yet in other areas would cause drought.

Shape memory alloys

Shape memory alloys are made of a mixture of metals, with the specific design that should they be deformed e.g. bent out of shape, they will retake their original shape (at least on macroscopic scale).  A common example of this are shape memory glasses.  In the video below you will see that the glasses easily return to their original shape, When frozen in liquid nitrogen the deformed shape exists until it warms back up to room temperature.

Over time repeated deforming of these alloys will cause them to stop returning to their original shape. Engineering scientists at University of Maryland in the US have developed a new alloys that have the ability to reform their original shape even after being bent 10 million times!  Click on the picture below to read the BBC News article.