Silicon Element Facts

Silicon element facts: Silicon atoms contain 14 protons and a varying number of neutrons in their nuclei. In their neutral state they possess 14 electrons. Silicon is a very common element and makes up over a quarter of the Earth's crust. The most commonly known form of Silicon is sand, which is mainly Silicon Dioxide, a covalently bonded lattice structure.

Silicon Element Facts: Isotopes of Silicon

Silicon Element Facts: The Electron Structure of Silicon

The 14 electrons of the neutral Silicon atom are arranged into subshells as follows: 1s2 2s2 2p6 3s2 3p2 giving a total of four electrons in the third, outer shell. As the outer shell contains a maximum of 8 electrons distributed into four evenly spaced pairs, we can draw the electron dot diagram for Silicon as shown to the left. This is a useful diagram as we will be able to use it to construct some of the structures Silicon commonly finds itself involved in.

The electron subshell structure of Silicon can also be represented far more accurately than that given in the over-simplified Bohr diagram at the top of the page. The diagram below shows the placement of the electrons in their respective subshells. The distance from the nucleus of these subshells is an indication of the energy level they represent; subshells further from the nucleus are of a higher energy.

Silicon behaves chemically in much the same way as Carbon which is to be expected, as it has the same number of outer shell electrons. Silicon can form extended covalently bonded lattices as well as molecules. Below are two examples of covalently bonded Silicon: first is Silicon Tetrachloride which is a discreet molecule, and secondly the covalently bonded lattice that is Silicon Dioxide, the primary component of sand. With Silicon Dioxide, look for the Silicon atoms that are bonded four ways; this how all the Silicon atoms are bonded throughout the entire lattice.

Of course, these structures are not really flat; they are 3 dimensional and follow the rules for molecule shapes laid out in the Valence Shell Electron Pair Repulsion theory, or VSEPR.

Silicon differs from Carbon in one significant aspect. The outer shell of Silicon is much further away from the nucleus than in Carbon. This means that the nucleus has a weker grip on those electrons compared to Carbon, which is commonly referred to as its electronegativity.

Under certain conditions the electrons in the bonds Silicon forms are able to become free, and Silicon can conduct electricity. This happens when the electrons receive the right amount of energy, effectively ionizing the Silicon atoms. This does not mean that a piece of Silicon will suddenly produce a current if it absorbs some energy. In order to achieve this it needs to be treated very specifically with other chemicals, a process that is called doping. This is fundamental to the operation of the photovoltaic solar cell.