Atomic Structure

Atoms are made up of Protons, Neutrons and Electrons

Inside every atom, there's a nucleus containing protons and neutrons. Protons and neutrons are both known as nucleons. Orbiting this core are the electrons. This is the nuclear model of the atom.

The following are the properties of electrons, protons and neutrons in the table:

Atoms are Really, Really Tiny

Each atom is about a tenth of a nanometer (1 x 10^-10m) in diameter. To give you that in context, you'd need to line up around 4 million iron atoms side by side to give you a line 1 mm long. If you think that's small, try the nucleus.

1. Although the proton and neutron are 2000 times more massive than the electron, the nucleus only takes up a tiny proportion of the atom. The electrons orbit at relatively vast distances.
2. The nucleus is only 10 000th the size of the whole atom - most of the atom is empty space.
3. If we were to shrink the Solar System (including poor rejected Pluto) so the Sun was the size of a gold nucleus, Pluto would only be half as far away as gold's first electron.

Isotopes have the Same Proton Number, but Different Nucleon Numbers

Atoms with the same number of protons but different number of neutrons are called isotopes.

• Changing the number of neutrons doesn't affect the atom's chemical properties.
• The number of neutrons affects the stability of a nucleus though.
• In general, the greater the number of neutrons compared with the number of protons, the more unstable the nucleus.
• Unstable nuclei may be radioactive and decay to make themselves stable.

~The Nucleon Number is the Total Number of Protons and Neutrons.

Powerful Alloys

Titanium Alloys

Titanium (Ti) is a lightweight metal which forms amazing alloys with aluminium, vanadium, tantalum, niobium etc. These alloys are hard while being light. Initially, they were used in aerospace and aviation for making aircraft bodies. But now more applications are being found in automobile and general engineering. For example, the Tata Chemicals factory at Mithapur (India) uses huge Ti-alloy vessels for processing caustic soda (sodium hydroxide), which will otherwise corrode stainless steels in seconds.


Ti-alloys are difficult to weld and cut, hence they have not edged out steels. But they rule the roost in bio-medical implants. Ti alloys are now common in making jewellery, golf-clubs, expensive watches... there's a lot that can be done!

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Hooke's Law

The Trampoline

Hooke's law deals with springs and equilibrium. A trampoline is essentially an elastic disc that is connected to several springs. As you land on the trampoline the springs and the trampoline surface stretches as a result of the force of your body landing on it. 
Hooke's law states that the springs will work to return to equilibrium. In other words, the springs will pull back against the weight of your body as you land. The magnitude of this force is equal to that which you exert on the trampoline when you land. Hooke's law is stated in the following equation: F = -kx where F is force, k is the spring constant and x is the displacement of the spring. Hooke's law is merely another form of potential energy. Just as the trampoline is about to propel you up, your kinetic energy is 0 but your potential energy is maximized, even though you are at a minimum height. This is because your potential energy is related to the spring constant and Hooke's Law.

Intro of Density

Different densities of fluids.

Density is something that affects many of our everyday decisions. Consciously or not, we make mental calculations of density every time we interact with the physical world around us. Can we slide that box? Can we lift that rock? 

People are often confused about the difference between weight and density. There is an old riddle which highlights this confusion: “What weighs more – a pound of feathers or a pound of lead?” The answer, of course, is that both weight same – one pound. However, feathers are much less dense than lead, and therefore take up much more space. Density is the ratio of an object’s mass to its volume. This means that to find density, you must measure an object’s mass and divide it by the amount of space it takes up. The standard units of density are [kg/m3], although other units are commonly used such as [g/ml], [g/cm3], or [kg/l]. 1 ml has the same volume as 1 cm3.