Compounds and Molecules Honors Chemistry/Biology 10 th grade Spring 2013

Ionic Compounds Hard and Brittle Solid at room temperature Very high melting point Conduct electricity if dissolved in water or another solvent. Formed between metals and non-metals Properties can be traced back to the atomic structure.

Ionic Compounds Formed when a positively charged ion is attracted to a negatively charged ion. Oppositely charged ions will attract each other, forming ionic bonds. The ratio of positive ions to negative ions must allow for all of the positive charge to cancel out all of the negative charge.

Example +2 Here we have positive and negative ions. The positive ions have a charge of +2. The negative ions have a charge of -1. We have 5 ions of +2 charge (Total positive charge = +10) and 10 ions of -1 charge (Total negative charge = -10). Overall charge of the ionic compound = 0.

Sodium Chloride Example Each ion is attracted to its neighbors which forms an interconnected network of bonds. This gives the molecule strength, which is related to its properties. Ionic compounds are also brittle. Putting pressure along an edge can interfere with the alignment of ions.

Why do ions form? Atoms want to attain a Noble Gas electron configuration, so in some cases they will gain or lose electrons to do so. For example: – Sodium can lose one electron to have the configuration of Ne, so it forms a +1 ion. – Chlorine can gain one electron to have the configuration of Ar, so it forms a -1 ion. – In the formation of Sodium Chloride, an electron is transferred from Sodium to Chlorine. –

Use the Periodic Table

Covalent Bonds = Molecular Compounds Formed between 2 non-metals. Caused by “sharing” of electrons, not transfer of electrons. Examples: H 2 O, CH 4, Cl 2