<p>NOTES: TYPES OF CHEMICAL BONDS Name______Date______Block______</p><p>What is a chemical bond?</p><p>. A strong attractive force between atoms in a compound</p><p> Ionic: attraction of ______</p><p> Covalent: attraction of the nucleus of each atom to a ______pair of valence electrons</p><p> Metallic: attraction of ______charged metal ions to the mobile valence electrons in the metal </p><p>The Octet Rule</p><p>. The Octet Rule:</p><p> Atoms will lose, gain, or share valence electrons until each atom achieves…</p><p> an ______of valence electrons</p><p> a total of _____valence electrons</p><p> a ______electron configuration</p><p>. The Octet Rule is our guiding principle in the formation of chemical bonds between atoms </p><p>Types of Bonds</p><p> Ionic: atoms lose or gain valence electrons, forming + and – ions, which are then attracted to one another because they are ______charged</p><p> Covalent: atoms ______valence electrons, the nuclei of both atoms are strongly attracted to the shared valence electrons, forming the bond</p><p>May be nonpolar (equal sharing) or polar (______sharing)</p><p> Metallic: the valence electrons of atoms in the metal are mobile, leaving the metal atoms with a ___ charge, the + charged metal ions are attracted to the free-floating ______</p><p>What determines the type of bond formed between two atoms?</p><p>. The “______” for electrons! </p><p>. Atoms play “tug of war” with electrons</p><p>. The ______of the atoms determines their “strength” in the tug of war</p><p>. Electronegativity is a measure of the tendency of an atom to ______a bonding pair of electrons.</p><p>. The Pauling scale is the most commonly used. Fluorine (the most electronegative element) is assigned a value of ______and values range down from there Consider two atoms…</p><p>. Atom A and Atom B form a bond… </p><p>What if atom B is a lot more electronegative than atom A?</p><p>. Sometimes one of the atoms is much stronger (more electronegative) than the other, and “wins” the electron- this results in a transfer of electron(s) to form ions, and thus an ______</p><p>. Consider a bond between two atoms, A and B. </p><p> In this case, the electron pair is dragged right over to B's end of the bond. A has lost control of its electron, and B has complete control over both electrons. Ions have been formed.</p><p>A+1 ------:B-1</p><p>What happens if B is slightly more electronegative than A?</p><p>. Sometimes one of the atoms is a little stronger than the other, but not strong enough to “win” the electron</p><p>. This results in ______sharing of electrons, which is a polar covalent bond</p><p>. B will attract the electron pair more than A does.</p><p>. That means that the B end of the bond has more than its fair share of electron density and so becomes ______. At the same time, the A end (rather short of electrons) becomes slightly positive. </p><p>δ+A------:---Bδ- </p><p>(note that δ is pronounced “delta” means “______”, so δ+ means slightly positive and δ- means slightly negative. The δ- will always be on the more electronegative of the two atoms) </p><p>. This is described as a polar bond (or polar covalent)- a covalent bond in which there is a ______of charge between one end and the other </p><p> in other words one end is slightly positive and the other ______. </p><p> The electron density lies ______to one atom than the other</p><p> Examples include most covalent bonds. The hydrogen-chlorine bond in HCl or the hydrogen-oxygen bonds in water are typical NOTES: TYPES OF CHEMICAL BONDS Name______Date______Block______</p><p>What happens if two atoms of equal electronegativity bond together?</p><p>. Sometimes the atoms are equal or nearly equal in their strength (electronegativity), and neither wins</p><p>. This results in ______sharing of the electron(s), and thus a nonpolar covalent bond</p><p>. If the atoms are equally electronegative, both have the same tendency to attract the bonding pair of electrons, and so it will be found on average ______between the two atoms. </p><p>A-----:-----B</p><p>. To get a bond like this, A and B would usually have to be the ______atom. You will find this sort </p><p> of bond in, for example, H2 or Cl2 molecules.</p><p>How to determine bond type</p><p>. The ______in electronegativity between the two atoms is what determines whether a bond is ionic, polar covalent, or nonpolar covalent</p><p>. To determine the bond type-</p><p> Look up the electronegativity values for the two atoms in the bond</p><p> ______to find the difference</p><p>Use the chart (next slides) to determine the type of bond</p><p>. Difference in electronegativity Type of Bond </p><p>0- 0.3 ______covalent </p><p>0.4- 1.0 moderately polar covalent </p><p>1.1- 1.7 very polar covalent</p><p>> 1.7 ______</p><p>% Ionic Character</p><p>. Bonds can also be described based on their % ionic character, which is another way to express the degree of polarity in the bond.</p><p> 100% ionic character would represent a purely ______bond</p><p> 0% ionic character would represent a purely ______bond Let’s compare ionic and covalent</p><p>IONIC:</p><p>• Transfer of electrons to form ions due to ______electronegativity difference between the two atoms</p><p>• Oppositely charged ______are attracted</p><p>• The ions build up in a 3 dimensional crystal lattice; there are not individual ______</p><p>• The chemical formula represents a ______: the lowest whole number ratio of ions that is neutral</p><p>POLAR COVALENT:</p><p>______sharing of electrons due to some electronegativity difference between the two atoms</p><p>• Electron clouds ______and electrons are shared unequally to form bond</p><p>• Individual molecules are formed</p><p>• The chemical formula represents a ______</p><p>NONPOLAR COVALENT:</p><p>• Equal sharing of electrons since the two atoms have ______or nearly equal electronegativities </p><p>• Electron clouds ______and electrons are shared equally to form the bond </p><p>• Individual molecules are formed</p><p>• The chemical formula represents a ______</p>