Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 1 Lewis Dot Symbols of Some Elements

Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 2 Ionic Bond Formation Magnesium has two valence electrons. It ionises two give a magnesium ion with two positive charges. These two electrons are captured by two fluorine atoms. In this way, both the cations and anions attain a noble gas configuration. Thus two ionic bonds are formed.

Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 3 Born-Haber Cycle for NaCl

Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 4 Hydrogen Molecule As the two atoms come closer, their 1s orbitals begin to overlap and both nuclei start to attract the two electrons. Each electron can now occupy the space around both atoms, i.e. the two electrons are shared by both nuclei. The attraction between the nuclei and the electrons holds the two atoms together. Of course, the shape of the combined orbitals and the electron density changes.

Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 5 Formation of Hydrogen Chloride Molecule 1bonding pair 3 lone pairs :: HCl : : An electron pair is either a bonding pair (an electron pair that is shared between two atoms) or a lone pair (an electron pair that is not shared between atoms).

Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 6 Multiple Covalent Bonds C : C H H H H :: : : : CC HH : : ::: EtheneEthyne Triple bondDouble bond

Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 7 Electronegativities of Elements

Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 8 Writing Lewis Structures Step 1: Count the number of valence electrons in PCl 3. PCl 3 1  5=5 e  3  7=21 e  We have a total of 26 electrons.

Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 9 Writing Lewis Structures P Cl Step 2: Arrange the atoms radially, with the least electronegative atom in the centre and place one pair of electrons between the central atom and each peripheral atom by drawing a bond between the atoms.

Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 10 Writing Lewis Structures P Cl        Step 3: Distribute the remaining electrons to the peripheral atoms to satisfy the octet rule.  

Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 11 Multiple Covalent Bonds P Cl           Step 4: Distribute any remaining electrons to the central atom. If there are fewer than eight electrons on the central atom, a multiple bond may be necessary

Chemical Bonding I – Basic Concepts General Chemistry I CHM 111 Dr Erdal OnurhanSlide 12 Extended Octet : F : : : F : : : : F : : P F : : :