Chemical Bonding

By the end of this lesson you will be able to: Name and describe the 3 types of bonds and how they are different List possible compounds in each and how elements are affected by the bonds they share Describe how we know these bonds exist. What are properties of the bonds?

Ionic Bonds Bond most often between a metal and a nonmetal Bond most often between a metal and a nonmetal Transfer of electrons from the metal to the nonmetal Transfer of electrons from the metal to the nonmetal Electrical attraction between large numbers of cations and anions called clusters Electrical attraction between large numbers of cations and anions called clusters Ion = a charged particle Ion = a charged particle

Ionic Bonds Cation = + charged particle Cation = + charged particle –Loves to give electrons away –Low Ionization Energy, Electron Affinity & Electronegativity –Typically are metals –Most metallic element = Fr

Ionic Bonds (cont.) Anion = - charged particle Anion = - charged particle –Loves to accept electrons –High Ionization Energy, Electron Affinity & Electronegativity –Typically are nonmetals –Most nonmetallic element = F

Ionic Bonds (cont.) If a bond is ionic: If a bond is ionic: – The compound is solid –The compound will fall apart (dissociate) into its original ions when dissolved in water -If a conductivity test is performed, the light bulb will… light! -EN values 1.8 up to 4

In General Ionic Bonds are the strongest bonds there are

Covalent Bonds Formed when 2 nonmetal atoms share electrons Can be liquid, solid or gas

Polar Covalent Bonds Unequal sharing of electrons Unequal sharing of electrons Electrons attracted more to higher E.N. atom Electrons attracted more to higher E.N. atom Electronegativity difference range = 0.3 – 1.7 (for polar covalent bonds) Electronegativity difference range = 0.3 – 1.7 (for polar covalent bonds) Polar Covalent Bonds dissolve in water Polar Covalent Bonds dissolve in water –Why? –(Check out page 19 in your packet for EN of water) The light bulb doesn’t light up. The light bulb doesn’t light up.

Non-polar Covalent Bonds Equal sharing of electrons Equal sharing of electrons Electronegativity difference range = 0.0 – <0.3 Electronegativity difference range = 0.0 – <0.3 Usually found between diatomic molecules – two of the same atoms Usually found between diatomic molecules – two of the same atoms Non-polar covalent bonds don’t dissolve in water. Non-polar covalent bonds don’t dissolve in water.

Metallic Bonds Bond formed between 2 metal atoms. Bond formed between 2 metal atoms. Excellent electrical conductors in solid state Excellent electrical conductors in solid state Electrons are free to move within electron clouds of all metal ions = Electrons are free to move within electron clouds of all metal ions = Sea of Electrons

Metallic Bonds In metals, p-orbitals and some d-orbitals are completely vacant and overlap each atom. In metals, p-orbitals and some d-orbitals are completely vacant and overlap each atom. Electrons are delocalized – they don’t belong to any one atom anymore. Electrons are delocalized – they don’t belong to any one atom anymore.

Quick Review Ionic bonds are between –A) metals and non-metals –B) non-metals –C) metals Answer A) metals and non-metals

Quick Review Covalent bonds are between –A) metals and non-metals –B) non-metals –C) metals Answer B) non-metals

Quick Review Metallic bonds are between –A) metals and non-metals –B) non-metals –C) metals Answer C) metals

Quick Review The strongest bonds are between –A) metals and non-metals –B) non-metals –C) metals Answer A) metals and non-metals (ionic)

Quick Review Ionic bonds at room temperature are –A) solid –B) liquid –C) gas –D) any Answer A) solid Can you name some?

Quick Review Covalent bonds at room temperature are –A) solid –B) liquid –C) gas –D) any Answer D) any Can you name some? HCl (aq), Bromine (aq), Fluorine (g), Diamond (s)

Quick Review Metallic bonds at room temperature are –A) solid –B) liquid –C) gas –D) any Answer A) solid and B) liquid What metallic bonds can be liquid at room temperature? Hg Any ideas why? Bond strength not enough to make a solid yet strong enough to keep it from being a gas.

Quick Review Which bonds are most likely to dissociate in water (water is polar) –A) ionic –B) polar covalent –C) nonpolar covalent –D) Metallic Answer A) ionic

Piecing It All Together The type of bond can be predicted by subtracting electronegativity values. –Nonpolar or polar? DifferenceBond Type X ≤ 0.3Non-Polar Covalent 0.3 ≤ X ≤ 1.7Polar Covalent X ≥ 1.7Ionic

22 Use the electronegativity difference to identify the type of bond between the following: nonpolar covalent (NP), polar covalent (P), or ionic (I). A. K-N2.2ionic (I) B. N-O0.5 polar covalent (P) C. Cl-Cl0.0nonpolar covalent (NP) D. H-Cl0.9polar covalent (P) Solution

Where to get the values?

Electronegativity difference Bond Type Zero Intermediate Large Covalent Polar Covalent Ionic Covalent Character decreases Ionic Character increases

Determination of Ionic Character Compounds are ionic if they conduct electricity in their molten state Electronegativity difference is not the final determination of ionic character

Bonding Spectrum

Hydrogen Bonds Intermolecular – attraction between molecules One molecule is polar and has Hydrogen in a H-F, H-O or H-N bond Other molecule has an unshared pair of electrons, usually F, O, N

Hydrogen Bond Example:

Van der Waals Bonds These bonds are important for Noble Gases Very weak bonds Electrons of Noble Gases get shifted to one side causing it to attract a slightly positive atom that is nearby.

Van der Waals Bond Example: