by Lime Red Tetrahedron

Created on: January 09, 2009

The nature of matter has challenged science since the beginning of time. In 450 BCE, the philosopher Democritus considered a question that has yet to be answered. To what extent can we define what exists? To what extent can we take the Universe apart? From this philosophy came the word atom from the Greek word atomos, meaning indivisible. Although we now know that the atom can be divided further, the name remains. The atom is the smallest unit of an element. For example, the smallest quantity of iron that can be obtained is a single atom of iron. If the atom were divided further, it would no longer be iron. The study of the atom and its characteristics is the focus of the entire science of chemistry.

More specifically, chemistry deals with the electronic configuration of the atom and the electronic interactions between them. The force that causes these interactions is known as the weak force. The weak force causes electrons to be attracted to the nucleus of the atom. This force extends beyond the atom itself, however, and attracts electrons from other atoms. When the atom's weak force is occupied with a certain number of electrons (determined by the element), the atom is said to be at a low level of energy. Atoms that are not at this optimal level of energy tend to interact in order to allow the most stable electronic configuration. These interactions are chemical reactions.

When atoms interact to achieve lower energy states, they tend to interact in two fundamentally different ways. The first of these means of interaction is through the formation of ions. Ions form when atoms gain or loose ownership of electrons. The increased or reduced number of electrons induces a charge on the atom. The atom can either be positively charged (caused by a decrease in the quantity of electrons), or negatively charged (caused by an increase in the number of electrons.) These charged atoms attract to atoms of opposite charge to form ionic compounds. This form of interaction forms extremely resilient bonds, causing ionic compounds to have massive melting points.

Atoms can also interact through covalent bonding. This occurs when the atoms do not differ as much in the nature of their electron configurations (more specifically, differing electronegativity.) Therefore, electrons are not transferred permanently from one atom to another, but instead alternate between atoms. The bonded electrons are attracted most strongly to the most electronegative atom in the compound, causing the

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