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Binary Molecular Compounds. The Third Category of Compounds – Binary Molecular What are Binary Molecular Compounds? These compounds contain two elements (binary). The term “molecular” indicates that these elements are joined by a covalent bond. They must therefore be nonmetals.
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The Third Category of Compounds – Binary Molecular What are Binary Molecular Compounds? These compounds contain two elements (binary). The term “molecular” indicates that these elements are joined by a covalent bond. They must therefore be nonmetals. Bottom line – 2 elements – both nonmetals To name and write formulas for these, you must know some numerical prefixes.
Naming – you must use prefixes. • 1 = mono 3 = tri 5 = penta 7 = hepta 9 = nona • 2 = di 4 = tetra 6 = hexa 8 = octa 10 = deca • Steps • The first nonmetal only gets a numeric prefix when there is more than one. No prefix if there is only one. • The second element always gets a numeric prefix and always has a suffix of -ide
CO2 Carbon dioxide CO Carbon monoxide N2O4 Dinitrogen tetraoxide H2O Dihydrogen monoxide CCl4 Carbon tetrachloride Name the first element. Since there is only one, no prefix is needed. The second element always gets a prefix and a suffix of –ide. Name the first element. Since there are two present, the prefix “di” is needed. The second element always gets a prefix and a suffix of –ide. Do you think it wise to BAN DHMO?
AlCl3 What do you think about this one??? Be careful. This is a metal and nonmetal. Always keep your Periodic Table in front of you for reference. You may have been tempted to say “aluminum trichloride”. This is INCORRECT! This is a binary IONIC compound. No prefixes are used. Simply aluminum chloride. Given the names of binary molecular compounds, how do you write the formulas? Very easy to do!!! The prefixes tell you how to write the formulas. DO NOT CONSIDER CHARGES. NONMETALS ARE ALL NEGATIVE SO TO USE CHARGES DOES NOT WORK!
Silicon dioxide Silicon and oxygen are both nonmetals. The lack of a prefix on silicon means that there is only ONE silicon. The prefix “di” in front of oxide means that there are TWO oxygens. SiO2 Diphosphorous pentachloride P2Cl5 Phosphorous and chloride are both nonmetals. The prefix “di” means that there are TWO phosphorouses (Is that a word?) The prefix “penta” before chlorine means that there are five chlorines.
Nitrogen monoxide Nitrogen and oxygen are both nonmetals. The lack of a prefix on nitrogen means only ONE nitrogen. The prefix “mono” on oxygen indicates ONE oxygen. NO Is this not sooooooo easy!??