1. Quick Quiz 1.Draw the lewis diagram for the following: a)Cl 2 b)O 3 c)C 2 H 4 2.What is the octet rule? 3.What are the two types of bonding and what is the difference between them? 1.Draw the lewis diagram for the following: a)Cl 2 b)O 3 c)C 2 H 4 2.What is the octet rule? 3.What are the two types of bonding and what is the difference between them?

2. Electronegativity Ionic Bonding Polarity

3. Electronegativity  Electronegativity describes how strongly the atoms of an element hold onto or attract electrons.  The kind of bond formed between atoms depends on the attraction each atom has for electrons.  Electronegativity describes how strongly the atoms of an element hold onto or attract electrons.  The kind of bond formed between atoms depends on the attraction each atom has for electrons.

4. Scale of Electronegativity  Similar to the star system for hotels, but 4 is the highest possible.  4.0 means the element has the highest attraction possible for electrons, and 1.0 has the lowest attraction for electrons.  Similar to the star system for hotels, but 4 is the highest possible.  4.0 means the element has the highest attraction possible for electrons, and 1.0 has the lowest attraction for electrons.

6.  Metals have low EN’s  Non-metals have high EN’s  F is the most EN followed by O and N  No atom has an EN of 0 because even the most reactive metal has some attraction for its electrons  Metals have low EN’s  Non-metals have high EN’s  F is the most EN followed by O and N  No atom has an EN of 0 because even the most reactive metal has some attraction for its electrons

7.  Electronegativity increases across a period and decreases down a group.  As you go down the PT, the number of shells increases and are therefore electrons are further away from the nucleus, and the attraction to outer electrons is smaller. [Shielding]  As you go across the PT, the number of electrons in one shell increases, therefore the attraction to the nucleus is greater.  Electronegativity increases across a period and decreases down a group.  As you go down the PT, the number of shells increases and are therefore electrons are further away from the nucleus, and the attraction to outer electrons is smaller. [Shielding]  As you go across the PT, the number of electrons in one shell increases, therefore the attraction to the nucleus is greater.

8. Ionic Bonding  When electrons are transferred between atoms, electrically charged particles called ions are formed and the force of the attraction between ions is known as an IONIC BOND.  This attraction is called electrostatic attraction which forms the IONIC BOND.  When electrons are transferred between atoms, electrically charged particles called ions are formed and the force of the attraction between ions is known as an IONIC BOND.  This attraction is called electrostatic attraction which forms the IONIC BOND.

9. Examples  Sodium and Chlorine

10.  Magnesium and Chlorine

11. Draw the diagram to show the ionic bond of the following 1.Sodium Fluoride 2.Sodium Bromide 3.Potassium Chloride 4.LiBr 5.KF 6.LiCl 1.Sodium Fluoride 2.Sodium Bromide 3.Potassium Chloride 4.LiBr 5.KF 6.LiCl

12.  When the metal reacts with the non-metal, millions of ions are formed. These oppositely charged ions attract each other and form regular patterns of positive and negative ions in a solid crystal form.

13. The ionic-covalent continuum  How do you work out whether the bond formed will be ionic or covalent?  Looking back at EN, If the difference between the two atoms is greater than 1.6, then one atom is much more strongly attractive to electrons than the other. The bonding electrons spend most of their time with the more EN element and we say the electrons have been transferred. [IONIC]  How do you work out whether the bond formed will be ionic or covalent?  Looking back at EN, If the difference between the two atoms is greater than 1.6, then one atom is much more strongly attractive to electrons than the other. The bonding electrons spend most of their time with the more EN element and we say the electrons have been transferred. [IONIC]

14.  If the EN is the same or similar (within 0.5) then the electrons are shared equally between the two atoms. [COVALENT]  SO… what happens when there is a moderate EN difference?  One atom is more strongly attractive than another, but the atom is still somewhat attractive.  If the EN is the same or similar (within 0.5) then the electrons are shared equally between the two atoms. [COVALENT]  SO… what happens when there is a moderate EN difference?  One atom is more strongly attractive than another, but the atom is still somewhat attractive.

15.  Electrons are shared between the atoms, but spend more of their time with the more attractive atom.  Since the electrons are unequally distributed, each atom ends up with a slight electrostatic charge.  The bond is said to have an electrical dipole and we call it a polar bond.  When the EN difference is between 0.5 and 1.6 a polar covalent bond is formed.  Electrons are shared between the atoms, but spend more of their time with the more attractive atom.  Since the electrons are unequally distributed, each atom ends up with a slight electrostatic charge.  The bond is said to have an electrical dipole and we call it a polar bond.  When the EN difference is between 0.5 and 1.6 a polar covalent bond is formed.

16.  We tend to think that covalent and ionic bonds are completely different, but they are really two ends of the same scale.  In a covalent bond the sharing of electrons is perfect.  In a polar covalent bond the sharing is uneven but still sharing.  In an ionic bond the sharing is so uneven it is called electron transfer.  We tend to think that covalent and ionic bonds are completely different, but they are really two ends of the same scale.  In a covalent bond the sharing of electrons is perfect.  In a polar covalent bond the sharing is uneven but still sharing.  In an ionic bond the sharing is so uneven it is called electron transfer.

17.  Non-polar bonds occur when the EN is the same. (I.e the atom is the same)  For example:  H 2, Cl 2 or Br 2  Non-polar bonds occur when the EN is the same. (I.e the atom is the same)  For example:  H 2, Cl 2 or Br 2

18. Recap -Two types of bonding: Covalent bonding; sharing electrons Ionic bonding; transferring electrons -Electronegativity is a measure of the attraction of an atom to its electrons. -Polar bonds form when electrons are unequally shared between the two atoms. -Two types of bonding: Covalent bonding; sharing electrons Ionic bonding; transferring electrons -Electronegativity is a measure of the attraction of an atom to its electrons. -Polar bonds form when electrons are unequally shared between the two atoms.