Atoms

The periodic table is the so called a-z of elements all of our known elements are comprised and placed into one table all placed according to their atomic number. The elements are organised also according to groups and periods, it is through this organisation that chemists are able to predict a elements behavior, due to the trends which are shown going across a period from left to right or down a group. We tend to see that elements become more reactive as we are to go down a group.

The element itself is just the the name of elements we are most probably familiar with, for example gold, oxygen and nitrogen they are just the the outer part of trying to understand chemistry. A atom is the smallest part of an element which can ever exist. A molecule is the smallest part of an element or a compound which can exist alone or under ordinary conditions.

For example chlorine exists as particles of Cl2 but only under ordinary conditions these can change depending upon different factors such as temperature.

The atom is the base of chemistry it defines our world and the universe, giving us the unique variety of elements. The atom is comprised of a central nucleus surrounded by clouds of particles known as electrons. With in the center of the atom, within in the nucleus this is where the particles known as protons and neutrons are found. These three particles are the basics of an atom, they are what holds the atom together, due to the charges that they hold.

     Particle       charge  

Electrons      -1

Protons        +1

     Neutrons    Neutral

Electrons are negatively charge
Protons are positively charge 
Neutrons are neutral


How many protons, neutrons and electrons


Lets take the element carbon to use for this example Carbon is situated in group 6 of the period table, the element is presented with a capital C, it has a number present at the bottom and at the top. The number at the bottom represents the atomic number this is the number of protons as well as electrons present, carbon has the atomic number of 6, meaning it has 6 electrons and 6 protons. The number on top is known as the atomic mass this is the mass of the element, this represents the number of protons and neutrons. In this case carbon has the atomic mass of 12, from the atomic number there is 6 protons so to find the neutrons we subtract the atomic number from the atomic mass, 12 - 6 = 6 meaning there are 6 neutrons present in carbon.

The atom has its clouds of electrons in so called shells, which orbit the central nucleus. It is only the electrons that take part in chemical reactions, protons and neutrons do not have any roll in a reaction. Although they contribute to atoms (or ion) overall charge.


Comparing the masses of atoms


In 1919 the mass spectrometer was invented, a device used to compare the masses of atoms, today they are mostly known as relative atomic masses. The mass spectrometer has 5 main stages that contribute into giving the relative atomic mass of an atom.

1) At first gases, liquids and volatile solids are injected into the instrument the sample is vaporized, this stage is known as Vaporization.


2) After vaporization the element passes into the next compartment the ionization chamber, here the the atoms are bombarded with a stream of high energy electrons. The idea is to knock electrons off of the atoms by using the beam of electrons, this will then cause the atoms to form positively charged ions. It is positive because there are more positively charged protons present in the atom at this stage than electrons making the overall charge of the atom +ve thus creating an ion, this stage is known as Ionization.

3) The next stage is the acceleration of ions, the ions pass through holes in parallel plate, an electric supplied here, this causes the ions to accelerate towards the next stage of the ionization chamber. This third stage is known as Acceleration.

4) The ions now enter a strong magnetic field, this field deflects the ions according to their atomic masses, lighter atoms are deflected more than heavier ones. This stage is known as Deflection. 

5) If the magnetic field stays constant and is not changed then ions with one particular mass will be able to hit the ion detector. Ions of a small mass will be deflected to much, ions with a much higher mass will be deflected too less, because of this the process will be repeated over again to get a new set of masses, while changing the magnetic field each time. This final stage is known as Detection.


 Electronic configuration


When atoms react the electrons are distributed, this may be so that electrons are either transferred to another atom or shared between two atoms.

When atoms lose an electron energy is required to remove electrons from the shell of an atom, this energy is known as Ionization energy.  


So how are electrons arranged in atoms?
Taking carbon as an example, we know that carbon has 6 electrons and that they surround the central nucleus. The way atoms seemed to be understood is by the electrons being in shells, the shells have a limited number of electrons that they can hold. The very first shell being the closet to the center of the atom can hold 2 electrons, the 2nd shell can hold 8 electrons, the third can also hold 8 electrons and so on and so fourth. This is the very basic understanding of electrons filling shells.

By studying ionization energy's scientists have concluded that shells also have sub shells. Meaning the shells of an atom are not always filled according to the 2, 8, 8, 8 shell filling.

• The first shell can have 2 electrons in the same sub shell
• The second shell can have 2 electrons in one sub level and 6 electrons in a slightly higher sub shell.
• The third shell can have 2 electrons in one sub level, 6 electrons in a slightly higher sub shell and then 10   electrons in a still slightly higher sub shell
• The forth shell can have  2 electrons in one sub level, 6 electrons in a slightly higher sub shell, then 10   electrons in a still slightly higher sub shell and 14 electrons in a still slightly higher sub shell.

the sub shells have names being s, p, d and f. 

s containing 2 electrons

p containing 6 electrons

d containing 10 electrons

and f containing 14 electrons

This is the idea of how atoms seem to have their electrons arranged, I do suggest some recommended reading "Chemistry in context" by Graham Hill and John Holman.