Download The topic that fascinated me the most in my Science lessons this

The topic that fascinated me the most in my Science lessons this year is the Periodic Table and its
power of predicting the existence and properties of elements yet to be discovered.
Dimitri Mendeleev placed the 65 known elements of his time into a grid table and observed gaps in
the table. Based on the position of gaps in the table, he predicted the existence of undiscovered
elements and their properties even before they were found. Subsequently, these elements such as
germanium, gallium and scandium were found and their physical and chemical ‘behaviour’ were just
as Mendeleev predicted! Hence, even though Mendeleev did not physically stumble upon these
elements, he could be said to have discovered them. Why is Mendeleev able to predict the
properties of undiscovered elements just by looking at the Periodic Table?
I learnt that this is because the Periodic Table is designed to classify elements based on their
observed chemical properties and their atomic number (number of protons). Hence, the Periodic
Table shows trends and patterns as we move horizontally across a Period and vertically across a
Group. The trends and patterns are captured in this version of the Periodic Table obtained from the
Internet:
Moving across the period, I noticed that each atom of the element has one more electron. These
electrons are arranged in a certain configuration consisting of layers called shells. The shell closest to
the nucleus contains only two electrons and the subsequent shells contain a maximum of 8 electrons.
The electrons in the outermost shell (also known as the valence shell) participated in chemical
reactions. Therefore, for a metal, how readily a metal atom surrenders its electrons depends on how
far away the negatively charged nucleus and how many valence electrons are there. The nucleus of a
bigger metal (e.g. magnesium) exerts a smaller pull on its valence electron because the valence
electron is further away. It therefore loses its electron readily to a halogen atom (e.g. chlorine).
Beryllium, a much smaller metal atom, can hold on to its valence electron when partnering a
chlorine atom because its valence electron is nearer to the positively charged nucleus. Therefore,
Beryllium forms covalent bonds where it shares the electron with chlorine.
An atom is happiest when its shell is fully filled and these atoms form the noble gases group. Every
atom aspires to become its closest noble gas, with the outermost shell fully filled with 8 electrons.
Hence, sodium, which has only one electron in its valence shell, is happy to give up its atom to
become similar to Neon. However, unlike Neon which is neutral, Sodium attains the electronic
configuration of Neon but is positively charged. Calcium is also quite happy to give up two electrons
to attain the electronic configuration of Argon. However, when the atom has 3 or 4 electrons, it is
more unwilling to give them up to a partner as that seems too much to lose for a partnership. So,
they prefer to share the electrons in a more equal, covalent-style relationship. Atoms are like human
beings, some more generous and some more selfish. I found this sweet little poem portraying ions as
lovers:
I am attracted to you
Like an electron to a proton
Together we form an ionic bond
Though we are opposite charged ions
I am drawn towards you
Our love is unique as an orbital
For only two electrons can fill this space
As my love for you increases
My energy level rises
I am in this excited state
Increasing the tendency to form a chemical bond
I was an element
It took you to make me a compound substance
Falling in love with you is a chemical reaction
Which cause my love for you to grow
Ours is an exothermic love
Each giving of love not just absorbing it
Sometimes you do something especially nice
Which speeds up the chemical process
Like a catalyst in my increasing love for you
I realise we have our inhibition periods
And sometimes I am selfish enough
To be an endothermic reaction
Only absorbing your love
The feeling i have for you is so intense
It cannot be measured in kilojoules
Often I have to make a qualitative elementary analysis
To understand and love you more
But i don't expect to know your empirical formula
You are too complex a person for that
WHEN YOU ARE GONE
I AM A NOBLE GAS
AN INERT SUBSTANCE
WHEN I AM WITHOUT YOU
THE WORLD SEEMS STILL
AND I AM AT EQUILIBRIUM...
Chemistry is so much fun!