How do atoms interact in ionic compounds and molecular compounds?

Answer 1

Ionic compounds are pure substances generally formed between metallic and non-metallic atoms. In these substances, the metallic atoms lose their valence electrons in order to acheive stability. These valence electrons are then transferred to the nonmetallic atoms. The transferred of electron from the metallic to the nonmetallic atoms allows all the atoms to acheive stability by the formation of stable octets (full s and p orbitals in the valence shell). Due to the loss and gain of electrons, the metallic and nonmetallic atoms become positive and negative ions respectively, The oppositely charged ions then attract. This attraction of oppositely charged ions constitutes an ionic bond. The metallic and nonmetallic ions then arrange themselves into a symmetrical crystal lattice structure. Thus, ionic compounds are crystalline, not molecular, in nature. Simple examples of ionic compounds include sodium chloride (NaCl), lithium fluoride (LiF), and aluminum oxide (Al2O3). Molecular compounds are pure substances generally formed between nonmetallic atoms. In these substances, the atoms acheive stability through electron sharing. Since all nonmetallic atoms need to gain electrons to acheive stable octets in their valence shells (and none are willing to lose valence electrons) the only solution is to share valence electrons. A molecule is formed when two or more nonmetallic atoms share valence electrons. For example, in a molecule of oxygen (O2), each oxygen atoms shares two valence electrons with the other oxygen atom. In a molecule of nitrogen (N2), each nitrogen atom shares three electrons with each other. Each shared pair of electrons constitutes a covalent bond. Therefore, the oxygen molecule, has two shared pairs (a double bond) and the nitrogen molecule has three shared pairs (a triple bond). In the water molecule (H2O), each hydrogen atom shares one electron with the oxygen atom and the oxygen atom shares one electron with each hydrogen atom. The water molecule contains two single covalent bonds. Molecular compounds may or may not be crystalline. Ice is a crystalline substance formed when H2O molecules arrange into an orderly 3-d structure at low temperature. The symmetry of the ice structure is highly influenced by the polar nature of the water molecule.

Answer 2

Ionic compounds dissolve by splitting into a cation and an anion and then are surronded by the appropriate part of the solvent. Eg. NaCl splits into Na+ and Cl- in solution. If we assume this is an aqueous solution, then the partially positive H's will orient around the Cl- while the partially negative O will orient around the Na+.

This is much the same for molecular compounds. The difference being that molecular compounds do not dissociate into a cation and an anion, rather molecular compounds tend to be polar or non polar. The saying goes for molecular compounds, like dissolves like, i.e. polar dissolves polar, etc. For Example, ethanol and water are both polar compounds therefore they will be soluble in each other.