Atoms
Matter consists of small particles called atoms.
Each element on the periodic table consists of atoms of the same type.
They basically consist of three parts. Protons and neutrons are found in the centre of the atom.
Protons carry a positive charge, neutrons do not have any charge. Circling the centre (the nucleus)
of the atom, the electrons orbit constantly in areas called shells, rather like planets would
orbit the sun. The electrons travel at the speed of light. Only 2 electrons
can fit in the first shell and then it is full, 8 can fit in the second shell and 8 also in the
third shell. Electrons are negatively charged particles. The proton and electron number is the
same, so there is no overall charge in the atom (ie the account equals zero).
Each element has a reference number called its atomic number. This tells us how many protons (and
also electrons) a particular element has. So an element with an atomic number of 3 has 3 protons
(and also 3 electrons).
Electrons (3e): Only 2 can fit in the inner shell so the 3rd electron occupies the next shell.
Nucleus (3p and 3n): Contains 3 Protons and 3 Neutrons.
If an electron is lost or gained, that's a different story. Losing an electron means
that the atom is down one minus charge and so has an overall positive charge. Gaining an electron
means that the atom is up one minus charge and, yes, you've guessed it!, it has an overall
negative charge.
3e -3
3p +3
CHARGE = 0
Lithium (Li)
2e -2
3p +3
CHARGE =+1
Lithium (Li+1)
Now, so you're asking - why lose or gain electrons?
Well, atoms are like some people, they don't particalarly relish having loads of energy;
they much prefer to be low-key and take the path of least resistance.
As long as the orbit is full then the atom is happy!
If however the orbit is not full, then the atom will try to become stable by throwing away or
grabbing electrons; this forms the basis of chemical reactions.
Atoms react with each other because they want to pawn off / collect electrons depending on
the situation they find themselves in.
Take our example above.
The atom has three electrons, a lonesome one in its outer shell.
The atom has two choices:
Look for seven electrons to become stable. Lose one electron.
The atom goes for the choice that requires least energy on its part,
i.e., it loses one electron and "hey presto!!" full outer shell and happy atom!
Carbon has an atomic number of 6: therefore, it has six electrons, protons and six neutrons.
We won't mess with the protons and neutrons because that's nuclear physics.
We're concerned with the six electrons. Carbon has 2 electrons in the first shell and 4 in
the second shell.
Carbon has a choice: Lose four electrons. Gain four electrons.
What-to-do?? What-to-do??
Well Carbon, in fact finds a third choice - find four other atoms that also need electrons
and share with them. That's why four is the magic number for carbon. When it shares electrons,
we say that carbon BONDS with other atoms. This type of bonding where electrons are shared is
called covalent bonding. To denote this for short we write it like this
Graphic:
Shorthand:
Each line represents a bonding site for carbon.
Hydrogen is the most basic element, it consists of a single electron and proton.
This Hydrogen atom needs 1 other electron to become stable
Here Carbon bonds with 4 Hydrogens (who each need one electron to become stable) and in so
doing, gets to share the 4 electrons with the Hydrogens. Both parties are satisfied with the
marriage and methane gas is made.
Each Hydrogen atom now has 2 electrons in it's outer shell. The atom is therefore stable.
The Carbon now has 8 electrons in it's outer shell. Therefore it too is stable.
The resulting compound is Methane (CH4) formed with Covalent bonding.
To return to the Mission Selector, click here or on the Mission Selector icon on the menubar.
Look for seven electrons to become stable.
Lose four electrons.
