Forming Molecules with Atoms
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This tiny drop of water is really made of millions of tiny molecules
And those millions of molecules are made up of tiny atoms, ah!
Can you believe it? Amazing!
It all starts with the atom!
In their natural state, an electrically neutral atom has the same number of
negatively charged electrons as it has positively charged protons
The protons are found in the nucleus and the electrons are located around the nucleus
The electrons are distributed in shells
The first shell can hold two electrons, the second can hold eight
And the third can hold eighteen
The electrons in the most outer shell of a particular atom
are called its valence electrons
Atoms react chemically in bond with other atoms
with these valence electrons
Atoms are real control freaks
They are always trying to fill their shells
If an atom has one electron in its second shell
It will try to lose one electron or gain seven
But let me tell you, it is much easier to lose one
With more than three valence electrons, it's easier to gain electrons
by sharing them with other atoms
Let's look at hydrogen
It's in the first group of the periodic table
It only has one electron in the outer shell
Just like all the other elements in the same group
Because elements in the same group
have similar chemical and physical properties
All of these elements bond very easily with other elements
that like to gain one electron
Hydrogen is a bit unusual since it only needs one electron
not seven, to fill its shell
Hydrogen is happy to share an electron with another atom to fill its shell
Take our drop of water for example
One water molecule is made up of two hydrogen atoms and one oxygen atom
The oxygen atom has six electrons in its outer shell or a valence number of six
It would love to gain two electrons
Each hydrogen atom has a valence number of one
And when the three of them get together
They really bond!!
Behold! the water molecule