Olevel Chemistry Notes: Atomic Structure

Olevel Chemistry Notes

TOPIC#2 :Atomic Structure

understanding Atomic structure is key to understand Chemistry.In Our everyday life we see various non-things around us our mobile phones, laptops, batteries, chairs, plastics etc. all of these things are essentially made up of Atoms! 

WHAT ARE ATOMS:

simply, an Atom is the smallest unit that made up any particular thing. For instnce, a common table salt is made up of Atoms ( two different atoms chemically joined together). hence, every different matter that exists in the world has different Atoms which are responsible for different chemical and physical properties of different matters. 

HOW ATOMS FOR DIFFERENT MATTERS ARE DIFFERENT:

For many years until 1800 it was a common thought that an Atom is Solid and had no building blocks of its own. however, over the years it had been discovered that Atom itself was made up of smaller particles. these smaller particles are called sub-atomic particles. 

An Atom has three sub-atomic particles: Electron, Protons and Neutron.  now, question arises that how do these smaller particles fit into an atom which is already  microscopic. 

STRUCTURE OF AN ATOM:

An atom is made up of a tightly packed Nucleus and shell or ring for beginners.

see the diagram above. In the center in there is nucleus which contains protons and neutrons. Protons carries the Positive charge and have the relative mass of 1 while neutrons are neutral and also has the relative mass of 1. whereas, electrons move rapidly in the shells or rings around the nuclues. Electron carries the relative mass of 1/1840 and carries the charge of -1.

now if you might be wondering about their relative masses that how did we came to know of their relative masses or why is mass of electron 1/1840 while proton or neutron have 1?? well, answer to these question is quite complicated for an O level student, besides your exmaminer doesnot expect from you to know this. you will study about it in great detail in your A levels.

WHAT IS PROTON NUMBER AND NUCLEON NUMBER:

A proton number is simply the number of Protons inside the nuclues of an atom it is also called the Atomic number. An Atomic number is represented by symbol Z. now one thing and one important thing to remember at this point is that ATOMS ARE NEUTRAL. therefore, number of Protons can also be used to deduce the number of electrons. For instance see the Preodic table there you see symbols of elements and along with these symbols you will find numbers written with them like in the picture below. here the atomic number is 2 which implies that helium atom has 2 protons consequently 2 electrons and 2 neutrons. how 2 neutrons?? well, Atomic mass= total number of Protons + total number of Neutrons

so,  4 = 2 + total number of Neutrons. now just do the maths and you will have your answer. 

A Nucleon number is total number of Protons and Neutron inside the nucleus of an atom. It is represented by A it is also called the Mass number. It is so called because mass of an atom depends upon number of protons and neutrons in the nuclues of an atom. while mass of electron is said or believed to be negligible.

now that we have seen the Structure of an atom we can discuss how atoms of different elements are different which constitute their different physical and chemical properties. the answer to the question is PROTON number. different elements have different Proton number and none of the elements have same proton number! these proton numbers or protons gives each element its unique characterstics.

ISOTOPES:                                                                                                                       Isotopes are atoms of same element with same nnumber of protons but different number of neutrons. isotopes have same number of electrons. hence, they have different NUCLEON NUMBER but same PROTON NUMBER.. during your study in  O levels and A levels they are very common so its good if become quite used to to this word and concept of ISOTOPES. most common Isotopes that you will be dealing with but not limited to are: Chlorine Isotopes, Bromine Isotopes, Carbon Isotopes and Hydrogen Isotopes.  Important characterstic to remember about Isotopes is that they have same Chemical properties but slightly different physical properties. their physical properties differ due to slight change in mass. 

~ if  you have any question related to the topic comment below  your confusion we'll try to respond at our earliest.