Chemical Substances and Bonds - Tips

The fractional distillation mixture separation process separates mixtures that have different melting points.

- Isotopes are atoms that have the same number of protons or same atomic number. However, it has different mass number.

- Hydrogen, Deuterium and Tritium are isotopes of hydrogen. They are isotopes because they have equal atomic numbers. They differ in mass number. Hydrogen has mass number 1. Deuterium has mass number 2. Tritium has mass number 3.

- Allotropes are substances formed by the same chemical element. There are oxygen allotropes, which are oxygen gas (O2) and ozone gas (O3). The difference in this case is the number of atoms in the molecule. Oxygen gas is colorless and ozone gas is blue.

- There are carbon allotopes: graphite carbon and diamond carbon. Diamond has the crystalline structure and is the hardest substance known. Graphite is easily worn and is therefore used for writing on paper.

- There are also allotropes of phosphorus: white phosphorus and red phosphorus. White phosphorus was widely used in bombs because it was very reactive. Burns easily in the air. Red phosphorus is a larger structure and is the result of white phosphorus.

- Allotropes of sulfur are: rhombic sulfur and monoclinic sulfur. They differ in their structure.

- Atoms bond to achieve stability, to acquire the electronic configuration of the noble gases.

- Noble gases are chemically stable elements. For this reason, they react with almost nothing, they are inert.
- In the ionic bond, the bond between metals and nonmetals prevails. The ions are joined by electrostatic attraction. Ionic compounds are solid at room temperature crystalline. They have a high melting and boiling point. Conduct electricity when in aqueous solution or molten.

- In the covalent bond the bond between nonmetals, hydrogen and nonmetals, and hydrogen with hydrogen prevails.

- In covalent bonding there is electron sharing. Follows the Octet Theory. For hydrogen, two electrons already serve for its stability.

- Covalent bonds form molecules. Ionic bonds form the so-called ionic aggregates. The metal bonds form the metal alloys.

- A covalent bond may be single, double or triple.

- There are three types of intermolecular bonds, namely outside the molecule. They are: Hydrogen Bridges, Dipole-dipole and London Forces.

- Hydrogen bridges are the strongest intermolecular bonds.

- Hydrogen bridges are responsible for the abnormal increase of the boiling point of water. Compounds capable of forming hydrogen bonds usually have higher boiling points and lower volatility. This is all due to their strong interaction, the bond is stronger.

- In hydrocarbons (organic compounds), the longer the carbon chain, the greater the number of interactions by Forces of London or Van der Waals. Then the higher the boiling point.

When a molecule has a polar part and a nonpolar part the nonpolar part is called hydrophobic and the polar part is called hydrophilic.

When a molecule changes from liquid to gaseous state, the intermolecular bonds rupture. Its structure is not changed.

- London Forces-type intermolecular bonds are the weakest and occur in nonpolar molecules.