Case study 1: There are over 100 elements in the period table that have different atomic structures. However there are some substances, such as graphite and diamond that have the same chemistry but different atomic structure. Substances that have the same chemistry but different atomic structures are called allotropes (). Carbon is the fourth most abundant element in the world. It usually is obtained from coal deposits but it must be refined for useful commercial use. The three known allotrops of carbon are graphite and diamond. Graphite is one of the softest materials known to man. It is usually used as a lubricant. It's produced by getting rid of black tar debris produced by petroleum coke after the refinement of crude oil. Graphite is also used in the production of steel. Graphite's most common use is the material used in pencils. Diamond is also another form of carbon. It is one of the hardest substances known. It's usually used for jewellery. Moreover, because diamond is hard and durable, they are ideal for cutting, grinding, drilling, and polishing. Very small pieces of diamond are embedded into grinding wheels, saw blades, or drill bits.
Table 1 shows the differences in physical properties of Carbon and Diamond (Elementalmatter.info)
Physical Properties
Carbon in Diamond
Carbon in Graphite
Melting Point
4726.85 C
5530 C
Hardness
Hard
Soft
Conductivity
Bad Conductor
Good Conductor
Reflects light
Yes
No
Damaged in hard conditions
No
Yes
Density
5.52 gm/cc
2.23 g/cm^3
Soluble
No
No
Both Graphite and Diamond are allotropes of carbon and as mentioned above, they have huge differences. So why is that? Graphite chemically has stronger bonds than Diamond, yet Diamond is stronger than Graphite. This all falls back to the atomic structures of diamond and carbon. Graphite contains two dimensional lattice bonds which means layers of carbon sheets. These bonds are really strong compared to the bonds that hold the sheets together, and therefore the layers are able to slide across each other making graphite a softer, more malleable material. Diamonds have 4 carbon molecules bonded to 4 other carbon atoms covalently. Covalent bonds are really hard to break. This is what makes diamond very hard. Moreover, graphite only has 3 shared electrons. The 4th one is free allowing electricity to pass through it. Diamond, on the other hand, has no free electrons and therefore cannot conduct electricity.
Case study 2 Elements in periodic three include sodium, magnesium, aluminium, silicon, phosphorus, sulfer, chlorine, and argon. Sodium is the 6th most abundant element on earth. It is usually never found alone as it is extreamly reactive especially with water and therefore has to be kept in a moist environment. It is also used in the cooling down of nuclear reactors. Magnesium is the 8th most abundant element on earth. Like sodium, magnesium is never found alone in nature. It is usually extracted from sea water and burns with a white light.
Some of an elements physical properties relate to their orbitals. But what are orbitals? It is impossible for us to know exactly were these electrons are going to be and therefore we cannot plot them. This is why it is said that atom has electrons spinning around it at specific region. These regions are known as orbitals. Each atom has different amounts of orbitals depending on the amount of electrons they have. For example, Hydrogen – if you plot all the places this atom can be found in, you will find its orbital.. 1s orbital. This region is found near the nucleus. The 1 represents the first shell, and the s represents the shape this region makes – a sphere. There are other orbitals known as 2s, 2px, 2py and 2pz. The 2s orbital is pretty much the same as the 1s orbital. The only difference is that it is further away from the nucleus and has more energy. The p orbital on the other hand, looks like two balloons joined together. Moreover, it points in a specific direction unlike the s
