Somries

Did you know two molecules can have the same chemical formula but different structures?

These are called isomers. They're made of the same number and kind of atoms, but arranged in a different shape such that it changes the physical properties of the substance. These can be seen most commonly in hydrocarbons (organic molecules) which contain long carbon chains. These carbon chains can be broken down so that they branch off a single main carbon chain, which changes its chemical properties.

All hydrocarbons including and after butane have at least one isomer.

n-butane is a straight carbon chain butane molecule, while isobutane branches off, seen above.

Molecules

...come in some funky shapes.

There are five basic types of molecular structures, that are dependent on how many bonds the compound forms.

The first kind is a linear structure. One element sits in the center, bound to two other elements on the side. Because of the VSEPR theory, the electrons want to be as far away from each other as possible because they repel. If each side element sits 180 degrees apart from each other, the molecule becomes balanced and a linear structure is formed.

The second kind is a bent molecule. When a molecule, such as H2O, is bonded, a lone pair is left over. Because there are now three groups of molecules, the side elements will separate out even further, to an angle of 105 degrees.

The third kind is a trigonal planar molecule. Three side elements will separate to form a 120 degree angle between each element to maximize the distance between each electron pair.

The fourth kind is a trigonal pyramid. When three side elements and a lone pair are present, the lone pair forces the elements into a tetrahedral shape, but it is called a pyramid because only the three side elements are present.

The final kind is a tetrahedron, mentioned earlier in the trigonal pyramid. Four bonded side elements will form a tetrahedral shape to balance out the molecule.

Polyatomic Ions

In addition to regular cations and anions, there are molecules called polyatomic ions!
These molecules are positively or negatively charged just like ions, except they are made of two or more elements. An example of these polyatomic ions include ammonium (NH4+), Hydroxide (OH-), Nitrate (NO3-), Nitrite (NO2-), Acetate (C2H3O2-), Sulfate (SO4-2), and Phosphate (PO4-3).

They bond to compounds such as ammonium chloride and acetic acid, where acetic acid is shown above.

Naming Compounds

This week we learned how to name Type 1 and Type 2 Binary compounds.

Type 1 Compounds are ionic compounds in which the ions are always a specific cation or anion of that element. They involve pairing metals, which always form cations, with nonmetals, which always form anions. These compounds have a balanced charge. For example, AlF3 is a compound in which Aluminum forms a cation with a +3 charge, while one Fluorine atom forms a -1 charge. Therefore three fluorine are required to balance this compound's charge. In addition, this compound is named aluminum fluoride. The metal always goes in the front of the formula, and the nonmetal follows, with the suffix -ide.

Type 2 compounds are compounds in which the ions formed may be variable, because there are several kinds the element can form. This is seen mostly in the transition metals, such as iron, which can form a cation with a +2 or a +3 charge. These are differentiated by a roman numeral after the name which signifies the charge: Iron (II) is the iron cation with a +2 charge. The method for naming compounds remains the same except for the roman numerals. FeO is iron (II) oxide.