Silicon: position in the periodic system and atomic structure
Silicon, Si, is an element of period 3, main group IV, atomic number 14, with electron formula 1s²2s²2p⁶3s²3p², four outer electrons and p-element status. In compounds it is tetravalent, with oxidation states –4 (Mg₂Si, SiH₄) and +4 (SiO₂). Its outer shell resembles carbon's, but the silicon atom is larger and its outer electrons are farther from the nucleus, so its nonmetallic character is weaker than carbon's. The Si–H bond is almost nonpolar, so SiH₄ shows neither acidic nor basic properties. Silicon is the second most abundant element in the Earth's crust after oxygen (about 27.6 % by mass) and occurs only in compounds: quartz and sand SiO₂, clay, feldspar, granite. It is obtained by reducing its oxide: SiO₂ + 2Mg → 2MgO + Si and SiO₂ + 2C → Si + 2CO (1500–1750 °C). Added to steel, silicon improves its magnetic and acid-resistant properties, while pure crystalline silicon serves as a semiconductor in electronic circuits and solar cells.
“C and Si table”: draw a two-column table in your notebook with rows for period, electron formula, oxide (CO₂ and SiO₂), hydride (CH₄ and SiH₄), state and uses. Fill it in your own words and compare with a classmate. Only a notebook and pen are needed.