双语教学 共价键.doc

Covalent bonding1. 教学内容Covalency ;2 kind of covalent bond; Lone pairs ;Coordinate bonds2. 学生情况Grade 11.The students should have already covered in previous lessons: atomic structure ,electronic configurations,Ionic bonding3. 教学目标Identify,define,and explain：the covalent bond,covalency,non-bonding,dative covalency Classify the two kinds of covalent bond.Distinguish non-bonding and coordinate bonds4. 专业术语Covalent bonding,electrostatic,nuclei,orbitals,overlap,Sigma bonds,Pi bonds,lone pairs,dative covalency,coordinate bonds5. 教学方法Lecture and experiment 6. 教学材料和资料Text Reference:Covalent bondingSection :3.3(page 17)7. 时间安排 45min8. 教学过程 (1) 准备 (2 min)Write out the key terms of this topic ,and read twice (2) 过程 (40min)1 引入Quick review of the ionic bonding: summary the characteristics of ionic bonding Start-up Problem: Is it the ionic bonding between two atoms in the H2 molecule? (Students discuss in groups of 5 and one representative shares his groupss opinions) We can conclude that the bond isnt ionic bonding。2 阐述 Definition: the Covalent bond First, we should know that the covalent bond is the bonding between two non-metallic atoms.Please pay attention to its application range. Let us look at its definition :A covalent bond is the electrostatic force of attraction that two neighbouring nuclei have for a localised pair of electrons shared between them. For example : H2 has been formed because the two H atoms share electrons .The atoms are said to be joined by a covalent bond.A covalent bond is formed between two atoms when the atoms share valence electrons. How to form a covalent bond? Covalent bonds form when the orbitals of two neighbouring atoms overlap so that both nuclei attract the pairs electrons between them. How do we classify covalent bond?(Students to take some examples of Sigma bonds and Pi bonds) Sigma bonds: When the orbitals from two atoms overlap along the line drawn through the nuclei ,a sigma bond forms. Pi bonds: Sometimes ,after a sigma bond has formed between two atoms,the p orbitals of the two atoms also overlap along above and below the line drawn through the two nuclei ,and another bond forms.(Examples-N2,C6H6,O3,CO2)Experiments With ball-and-stick model ,teacher demonstrate The formation process of two kind of covalent bond. Definition: Covalency Usually ,the number of bonds formed is known as the covalency. Further explanation: To form a bond an atom usually needs an electron to put into the bond and a space in an orbital to accept the electron from the other atom. In the combination of the table of the elements in the second period in textbook , teacher explains the definition of covalency.Definition: Lone pairs The pairs of electrons which are not shared,but belong only to one central atoms. Refer to the table of the elements in the second period ,you can find in the last four there are pairs of electrons which are under the control of only one atom.Pairs of electrons like this are called lone pairs.For example,Definition: Coordinate bonds Both the electrons in a covalent bond come from only one of the atoms.This is called dative covalency and the bond is called coordinate bond. (Examples-NH4+,H3O+)For example,3 总结 What is material with Sigma bonds? W