Tag Archives: chemistry

ORGANIC CHEMISTRY

CARBON and ORGANIC CHEMISTRY

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We are going to use the Periodic Table to talk about a very important element, which is Carbon, one of the stars of modern chemistry because is present in almost every compound  around us. Carbon itself is the principal protagonist of the part of Chemistry called Organic Chemistry.

 

Carbon is located in Group 4A of the Periodic Table of the Elements, that means this Element will be forming compounds sharing until 4 electrons.

Carbon and Organic Chemistry are present in different kind of materials for example in paints, rubbers, oils (and all petrochemical derivates), plastics (polymers of carbon), and even in Steel forming alloys with  metals.

In live organisms Carbon is part of the skin, hair, blood (as amino acids and proteins), fats (or lipids), carbohydrates such us glucose, DNA, RNA, vitamins, and carbon dioxide, that is why is important for Pharmaceutical  and Food industries.

Carbon is also present in graphites (as in pencils) and diamonds.

Organic Chemistry is based in an element called Carbon.

How Carbon is present in all different compounds?

There are two principal characteristic of this Element, that make him different and special from other Elements:

1st) When form compounds, they share electrons, that means that they don’t take or give electrons (they do not create ionic bonding). They form covalent bondings

2nd) They are able to share until 4 electrons. Most Elements win or take less than 3 electrons.

Now, we’ll try to see How Carbon creates compounds

We know that Carbon has 4 electrons in its valence shell, these electrons are in orbitals, one electron in one orbital.

The orbitals are around Carbon, not forming 90º or 180º  among them, but 109.5º in all cases.

To complete each orbital we need 1 electron, that can be provided for an Hydrogen for example. If that is the case, one Carbon will need 4 Hydrogens, and the final molecule is Methane, CH4.

A better representation of, methane, is this. One Carbon surrounded by 4 Hydrogens at the same distance and same angle among them.

When Carbon wants to create a bigger molecule, it replaces one Hydrogen for another Carbon and complete the other bondings with other atoms, as Hydrogens or another Carbon.

For example, when in a molecule we have 3 Carbons, then we will need 8 Hydrogens, and in that case the molecule is called Propane.

SOLUTIONS

DISSOLUTION

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It is the process by which a solute (solid, liquid or gaseous) in contact with a solvent is dispersed forming a mixture in which the components are not distinguishable. The best example of a solution is a salt dissolved in water, the most common salt is the one we use every day at the table by the time we eat, this salt has a crystal form, is composed of ions sodium positively charged, and ions chloride with negative charge.

When a salt crystal is in contact with big amount of water, ions Chloride, negative charged, will be attracted by the positive side of water which are the hydrogen atoms, they take the ions from the crystal lattice, and the original solid pass to same state of the solvent.
The final mix is homogeneous and have the same properties in the whole mix.

In Chemistry is important to know the amount of solute in a solution, this value is known as Concentration of the solution. The concentration of a solution is calculated using

Concentration\text{ of Solution = }\tfrac{Amount\text{ }of\text{ Solute}}{Amount\text{ of Solute + Amount of Solvent}}

Example:
Molarity\text{ = }\tfrac{Moles\text{ }of\text{ Solute}}{Volume\text{ of Solution}}

Next chapter will show different ways to express concentration of solutions.

MOLECULES

WATER POLARITY

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Water is one of the most important molecules in human life, not only because makes up more than two thirds of human body weight, but also because all the cell and organ functions depend on water for their functioning. Something similar occurs in animals and plants. This means that without water most kind of life on earth would disappear in a few days.

Water is composed of one Oxygen atom and two Hydrogen atoms. Oxygen has six electrons in its valence shell, and needs two electrons to acquire great stability, those two electrons are taken from two Hydrogen atoms.

The molecule of H2O is a three dimensional structure, Oxygen is the centre of the molecule, around him there are two pairs of electrons, and two Hydrogen atoms with angles around 107º among them.

Polarity

Oxygen and Hydrogen have electronegativity values of  3.5 and 2.1 respectively, when they are bonded the shared electrons are attracted to the Oxygen side, leaving the Hydrogen atoms with a slightly positive charge, and producing a final polar molecule.

When a water molecule is surrounded by another water molecule, they will interact each other through those slight charges. This interaction is called “Hydrogen Bonding”, which is a weak electrostatic attraction between slight positive and negative charges of different molecules.

MOLECULES

NON-POLAR BOND

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In a Non polar Covalent Bond, atoms share their electrons equally. That happens when, they have the same electronegativity or the same electron affinity. The best examples for this  kind of bonds are molecules created through the union of atoms of the same element, as in H2, N2, O2, Cl2  

When non-polar molecules interact among them, there are negligible forces of attraction, and they remain as individual molecules, that means these substances are gases.

In our environment we have these substances in the Air, which has approximately the following composition, 78% of N2, 21% of O2, 0.9% Ar (noble gas)

 

 

MOLECULES

IONIC BOND

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CHEMICAL BONDING

Atoms in our planet are not by themselves, they are joined at least to another atom through a chemical bond. Bonds allow atoms achieve a stable electron configuration, similar as the noble gases, which are mostly not joined to other atoms.

The more important kind of bonds are Ionic and Covalent.

Ionic Bond

Is formed between atoms from the groups IA, IIA (metals) and VIA, VIIA (non metals). In this bond,  metals donate one or more electrons to the non-metals leading to form ions, one of them positively charged (cation) and the other with negative charge (anion).

For example, common table salt is Sodium Chloride. When Sodium (Na) and Chlorine (Cl) are combined, the sodium atoms lose an electron, forming cations (Na+), and the chlorine atoms gain an electron to form anions (Cl–).

Na + Cl =  Na+ + Cl– = NaCl 

Most of the Ionic compounds in our planet are in the solid state and form lattice structures. The two principal factors in determining the form of the lattice are the charge of the ions and their sizes.

 

ATOM

ATOMIC RADIUS

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The atomic radius is the distance between the nucleus to the boundary of the surrounding cloud of electrons.

Atomic radii vary in a predictable and explicable manner across the periodic table. The radius increases moving down a group due to the addition of a new energy level or shell.

The atomic radius generally decrease along each period of the table, because although more electrons are being added to atoms, they are at similar distances to the nucleus (same shell), and the increasing nuclear charge “pulls” the electron clouds inwards, making the atomic radii smaller.

The noble gases have full valence electron shells, corresponding to an electron configuration s2 p6, making them very stable and not following the exact behavior than other atoms in the neighborhood.