Basic Information on Atoms

Atoms are very small particles which form the basic building blocks of everything around us.

The ‘magic numbers’ in chemistry are 2, 8, 8 which are the maximum numbers of electrons that can fit into the first, second and third shell.

Tip – When you draw the electrons on a dot and cross diagram try to draw them in pairs as it makes it easier for us to count how many electrons are in each shell. If you do not do this, then it becomes harder to know how many electrons you have drawn and you run the risk of miscounting the electrons and putting more electrons than you should be. (Electrons also move around in pairs, so by drawing them like this it makes the diagram more realistic).

atom

We can work out how many electrons would be in the outer shell of a particular element by looking at the periodic table and by looking at the proton number. With atoms (not ions) the number of protons in the nucleus is always equal to number of electrons in that particular atom.

Lithium has a proton number of 3 so this means there are 3 protons in the nucleus and 3 electrons in the atom’s shells.

The element’s aim is to become stable during its life. An element becomes stable when its outer shell is full of electrons. (Elements want full outer shell, we need to keep this in mind when we draw our dot and cross diagrams).

Covalent molecules – A covalent molecule is when we have 2 non-metal atoms. We can tell if an element is a metal or non-metal by looking at the periodic table and which side it is on of the baron step.

If we need to draw a dot and cross diagram of CH4 we would need to think about the electron configurations (2, 8, 8) of the elements in that bond.

So carbon has 6 electrons (2 in its first shell and 4 in its outer shell, this means that it needs 8 electrons to have a full outer shell, so it will need 4 more electrons). A non-metal element would gain electrons by making a bond and each time the atom forms a bond it gets an additional electron. This means that carbon needs to make 4 bonds in order to get a complete outer shell. As carbon always will have 4 electrons it will always need to create 4 additional bonds. This means that we can determine how many bonds an element will need to make by simply looking at how many electrons that element needs in order to get a full outer shell.

atom 2

Tip – When drawing covalent bonds do not draw the electrons in pairs, instead draw them separately as these electrons will overlap the orbit of a different electron. When a carbon atom and a hydrogen atom stick together (bond together) their orbits will overlap and both of these atoms will share an electron. Hydrogen requires 2 electrons to be stable so it shares an electron with carbon. The formula CH4 has the number 4 because it needs to make 4 bonds to become stable.

Another example would be CO2 the carbon atom needs to make 4 bonds, but the oxygen only needs to create 2 as it has 6 electrons in its outer shell. Each carbon atom needs to make 4 bonds while oxygen needs to make 2 bonds. We would be making a double if two oxygen atoms bond together. In a single bond each element shares a single electron. In a double bond each element shares 2 electrons.
The electrons that do not overlap in a covalent bond are known as ‘unbonded pairs’ or ‘lone pairs’.

Ionic bonds – An ionic bond is when a non-metal atom bonds with a metal atom. Remember – Always a non-metal atom will take electrons from a metal atom. For example NaCl – a chlorine atom will take an electron from the sodium atom so they will both have a full outer shell, which means they are stable.

An electron has a charge of -1 so if a chlorine atom gains an electron it becomes negatively charged. If the sodium atom loses an electron it becomes positively charged.
Another example would be MgO. A magnesium atom needs to lose 2 electrons to become stable while oxygen needs to gain 2 electrons to become stable.

An interesting fact to finish off with… Did you know there are more atoms in a single glass of water than all the glasses of water from the whole of the Earth’s oceans.

Thank you for reading.

What is a Maillard Reaction?

The Maillard reaction is a type of ‘nonenzymatic browning’ which is slightly similar to ‘caramelisation’. The Maillard reaction often results due to a chemical reaction between the amino acid and a reducing quantity of sugar (this usually requires heat).

The Maillard reaction is extremely important in the preparation, presentation or the baking of many and various different types of food. This type of reaction was named after a famous chemist known as Louis Camille Maillard, who first described this in 1912 while he was attempting to reproduce biological ‘protein synthesis’.
The type of amino acid is vitally important as it will often determine the flavour as a result. This reaction forms the basis of the flavouring industry.

In the process, hundreds of different flavour compounds are produced. These compounds, in turn, break down to form even more new flavour compounds, and this will continue. Each type of food has a rather distinctive and particular group of flavours compounds that are formed during the Maillard reaction.

Boiling food in water does not tend to allow the reaction to take place, as the boiling point of water (100 degrees Celsius) in far to low to set off the reaction. Frying foods in vegetable oils will often reach temperatures ranging from 180 degrees Celsius to 210 degrees Celsius, providing these temperatures are maintained the reaction will occur.

The brown crust of bread and the appetising crisp outside of chips are all the result of the Maillard Reaction.

Thank you for reading.

Animal Fact File: The Polar Bear

The scientific name for the polar bear is ‘Ursus Maritimus’. The polar bear inhabits much of the Arctic, Northern Canada and Northern Alaska. The polar bear is rare at the very north of the Arctic (commonly known as the Arctic basin) this is due to the fact that seal which are the primary food source for polar bears are only found in very low numbers. A male polar bear can weigh around 600 kg while females weigh 350 kg. Due to the hostile conditions that the polar bear inhabits human encroachment is less of an issue; this means the polar bear has been able to keep much of its range (over 85%) which is more than any other carnivore on the planet.

The polar bear has many adaptations these include:

1) Capable of eating large quantities of meat – A polar bear can eat 20% of its entire body weight in a single meal. This is a helpful adaptation because this helps the polar bear to cope for long periods of time without food. Also by eating vast amounts of meat it helps the animal to put on as much fat as possible as this helps to keep the polar bear warm during the bitterly cold winters of the Arctic.

2) Thick fur to protect against the cold – A polar bears coat is 3 cm thick, to keep the polar bear warm. The polar bear also has over 10 cm of fat (blubber).

3) Dark coloured skin – Although the polar bear may appear to be white its skin is actually black. The polar bear’s black skin is designed to absorb the sun’s rays to help to keep the animal warm, (especially during the winter months).

4) An excellent sense of smell – The polar bear has around 100 million sensory receptors in its nose, while a human has a mere 10 million. This means that the polar bear is more than capable of detecting the scent of its prey from up 2.5 miles away.

5) Short and curved claws – Polar bears have strong and curved claws which are used to grip into the ice to prevent them from slipping on the ice.

6) Very strong shoulders – When hunting seals that are under the ice the polar bear will often break the ice (which is often very thick about 1 – 2 meters) with an enormous amount of force using their front paws. The force that is used by the bear is more than enough to dislocate the shoulders of the average human.

7) White (hallow) fur – Polar bears have white fur to blend into their environment so, they can hunt more easily and to reflect any heat loss from the skin back into the body.

8) Small ears and tail – Polar bears have small ears and a small tails to minimize the concentration of heat loss.

9) Very large paws – The polar has very large paws in order to spread out its weight over the ice (this prevents the ice from breaking).

10) Capable of reducing its metabolism – The polar bear will often reduce its metabolic rate in the winter, this enables the animal to survive when food is in short supply.

11) Although the polar bear is the most carnivorous of all the bear species, it is capable of eating a wide variety of vegetation if there are not enough seals to find.

The reason why brown bears are closely related to polar bears is because the polar bear apparently evolved from brown bears. Around 6 million years a small population of brown bears visited the Arctic to hunt for seals. However the elements prevented them from leaving the Arctic. This population of ‘brown bears’ became smaller as they began to die out, but some were able to survive … and thrive. By 3.5 million years ago these ‘brown bears’ evolved into the modern day polar bear.

The polar bear is an excellent swimmer and can often be seen over 150 miles away from land or ice. The polar bear’s body fat helps keep it afloat and can swim at around 6 mph. On land the bear can cover vast distances in its search for seals. The polar bear can reach speeds of up to 30 mph and can maintain that for nearly 3.5 kilometres. The polar mainly eats seals (such as ringed and bearded seals) along with narwhals, beluga whales, reindeer, bird’s eggs and even walruses. Also the polar bear is the only predator that will kill humans for food.

Female polar bears that are due to have cubs will enter a semi-dormant state after entering their dens during October; the cubs are usually born in January. They emerge in early April with the female having eaten nothing for 6 months. The female waits until her cubs are able to walk for long distances, after which they walk to the sea hunt seals. The mother will care and protect them for 3 years until they leave. The polar bear is very adaptable and is the largest and most powerful predators in the world, wolves and brown bears will often avoid adult polar bears, but will kill young cubs. The polar bear has a life span of no more than 25 years. The polar bear is classified as an ‘Extremophile’ as it is capable of surviving in its hostile environment.

Thanks for reading.

The Discovery of the Electron

The idea of atoms existing was put forward by the famous Ancient Greek philosopher Democritus who thought that everything around us was made up of minuscule particles.
Democritus thought that by cutting an object could he could continue cutting it continuously. He concluded that this was not possible as there would be a piece that would be far too small to cut. Democritus also thought that these very small pieces (particles) were the basic building blocks of everything around us.

The word ‘atom’ comes from the Greek word ‘atomos’.
In the beginning of the 19th century John Dalton showed that atoms actually existed. He found out that there were atoms for every single element in the periodic table. During this time they did experiments with electric currents. These experiments involved obtaining the electric current and passing it through a gas.

In the 19th these scientists built glass tubes which had metal contacts on each end and got rid of most of the air in the tube and put an extremely high voltage between the metal contacts. If there was a wire between the metal contacts the electric current would have flowed through the wire, however the current had to go through the small quantity of gas still in the glass tube, and this caused powerful and spectacular arrays of glowing lights.
What happened was electric currents were being forced through the gas which was hitting the atoms of the gas which shook them to form light.

As technology improved better vacuums were made which were capable of getting rid of all the gas in glass test tubes. JJ Thompson passed an electric current through the vacuum which hit the glass and created a small green speck. When Thompson used magnets the green speck would move and also when he applied a voltage to the glass tube the speck would move again. Also when he used both of them at the same time the speck would stay still (he balanced the electric and magnetic force).

JJ Thompson was head of the ‘Cavendish Laboratory’ in Cambridge where he carefully studied the electrical beam which is known as a ‘cathode ray’. In the modern era the ‘Cavendish Laboratory’ has all the equipment that Thompson ‘apparently’ used for his experiments including the ones which he used to discover the electron. The word ‘apparently’ is used because he was not necessarily good at carrying out experiments.

On one of the apparatus there is a small disk made of metal where electrons were emitted. At first Thompson was unsure what this beam of light was, so he changed the material of the cathode to see if it was the property of cathode material. He also changed the number of gas particles in the glass tube. However each time he changed the variables of the experiment he still saw the green light, this meant that this was caused by the property of the matter not the material.

This concluded that these are charges of negative electricity which was carried by particles of matter.

Although Thompson had influenced the discovery of the electron, there were other scientists who were carrying out a similar experiment. In Berlin a German physicist was doing a more effective experiment unfortunately he misinterpreted his results. He thought that the beams of light in his tube were the flow of matter however he did not think that these were individual particles.
The electron was discovered in 1897.

Soon after the electron was discovered an American physicist Robert Millikan was able to calculate the electron’s charge and mass. He found out that the electron has a negative charge and was about 2000 times lighter than the smallest atom.

JJ Thompson thought that if there are electrons which have a negative charge in an atom then there must be a positive charge as well to counteract the negative charge. He put forward his idea of the ‘plum pudding model’. This meant that the electrons were meant to be surrounded by a circle of positive matter. This was what people thought the atom looked like towards the end of the 19th century.
However this idea was altered by Ernst Rutherford who came from New Zealand. In 1907 at Manchester Rutherford set up a famous experiment, this was where a small machine would expel (shoot) out alpha particles which would come into contact with a very thin foil of gold. Rutherford discovered that 1 in 8000 alpha particles were deflected back from the gold foil. Alpha particles are large and positively charged. This means that the alpha particles have hit a positive atom in the gold foil which causes them to be repelled.

Rutherford though that these atoms must have had a positive centre. After several experiments involving many different kinds of atoms Rutherford concluded that the atom consisted of a positive nucleus with negative electrons on the outside. This idea was similar to a solar system with the electrons orbiting the nucleus at the centre; this means that atoms are mostly empty space.

Electrons are loosely attached to the atom. This is important for technology which makes the electron the most useful subatomic particle. The electron can be useful for motors and electricity.

In 2008 a group of scientists from Sweden recorded the electron in motion which happens to be similar like a hummingbird flapping its wing.
The human understanding of electrons has allowed us to improve our technology and produce items such as computers and lasers.

This experiment could allow us to see inside electrons and molecules which would give us tools such as controlling a chemical reaction.

The atom has ‘sub-structure’ and we can fill its inner workings. Electrons are fundamental particles, but protons and neutrons are not. Protons and neutrons are composed of smaller particles known as quarks.

Thank you for reading.