Giant Covalent Molecules: Structure, Properties, and Comparison of Diamond and Graphite, Lecture notes of Chemistry

Download Giant Covalent Molecules: Structure, Properties, and Comparison of Diamond and Graphite and more Lecture notes Chemistry in PDF only on Docsity!

Giant covalent molecules

Describe the structure of giant covalent molecules Explain the properties of giant covalent structures

Giant covalent molecules

Review Small covalent molecules such as O , NH and CH have low melting and boiling points. These properties are because they have weak intermolecular forces. Properties of giant covalent molecules Giant covalent molecules consist of millions of atoms joined together by covalent bonds. Examples of giant covalent molecules include diamond, silicon dioxide and graphite. Giant covalent molecules are solid at room temperature. They always have high melting and boiling points. Diamond Diamonds are formed from carbon. In diamond, each carbon forms four strong covalent bonds. Diamonds have huge numbers of covalent bonds which have to be broken when diamond sublimates (approx 3,700 C). carbon Silicon dioxide Silicon dioxide contains the elements silicon and oxygen which are covalently bonded. silicon oxygen Silicon dioxide has a high melting and boiling point. Like diamond a large number of covalent bonds need to be broken for silicon dioxide to melt. Diamond does not conduct electricity. There are no free electrons to carry an electrical charge. The electrons in the outer shell are used to form covalent bonds. Silicon dioxide does not conduct electricity as there are no free electrons to carry an electrical charge In the exam, you will NOT be expected to draw these molecules, but you would be expected to identify them and explain their properties. (^2 3 )

T-

o

k

E1 (^) 1II 0

° old

• E

I.

§ (^) ⑨

*o÷¥¥¥→