Chemical Bonding

By the end of this lesson you will be able to: Name and describe the 5 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?

Covalent Bonds Formed when 2 atoms share electrons Occurs most often between nonmetals

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? 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. Can be a solid, liquid or gas Can be a solid, liquid or gas

Ionic Bonds Bond most often between a metal and a nonmetal Bond most often between a metal and a nonmetal Electrical attraction between large numbers of cations and anions Electrical attraction between large numbers of cations and anions 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!

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.

Hydrogen Bonding (pg 23 of your packet) Intermolecular forces – attraction between molecules Intermolecular forces – attraction between molecules Some H containing compounds are extremely polar Some H containing compounds are extremely polar –HF, H 2 O, NH 3 –Large EN differences cause this The hydrogen atom in the molecule is attracted to the unshared pair of electrons on another molecule The hydrogen atom in the molecule is attracted to the unshared pair of electrons on another molecule

Hydrogen Bonding

Van der Waals Bonds These bonds are important for Noble Gases These bonds are important for Noble Gases Electrons are in continuous motion and at any instant the electron distribution may be slightly uneven Very weak bonds Very weak bonds Electrons of Noble Gases get shifted to one side causing it to attract a slightly positive atom that is nearby. Electrons of Noble Gases get shifted to one side causing it to attract a slightly positive atom that is nearby.

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) covalent –C) metallic –D) all Answer A) ionic

Quick Review So why do we generally consider ionic bonds stronger when they can be dissociated by water? Doesn’t that make covalent stronger since they can’t dissociate in water? The key words here are generally and “stronger”. Lets use the table on page 19 to figure this out

Electronegativity and Strength 1) Find the EN values for each element 2) Subtract the lesser value from the larger (so the value is positive) 3) Who has the bigger number? Did the ionic (metal-non-metal) bond win or did the other?

Electronegativity and Strength 1) Find the EN values for each element –Na -> 0.9 –Cl -> 3.0 –O -> 3.5 –H -> 2.1

Electronegativity and Strength 1) Find the EN values for each element 2) Subtract the lesser value from the larger (so the value is positive) – =2.1 – =1.4

Electronegativity and Strength 1) Find the EN values for each element 2) Subtract the lesser value from the larger (so the value is positive) 3) Who has the bigger number? Did the ionic (metal-non-metal) bond win or did the other?

Types of Bonds Your turn Please complete the handout “bonding review sheet” for homework Use the periodic table with electronegativities to help you find the electronegativity difference Polarity describes if it dissociates in water