Compounds & Bonds – Unit 5 Why do atoms bond to form compounds? How are bonds formed? How do we represent compounds (names and formulas)?

Bonding Essentials Bonds are formed when valence electrons are gained, lost or shared by atoms There are 3 major types of bonds Ionic, Covalent, Metallic Compounds are 2 or more atoms bonded together, with different properties than their elements.

Chemical Bonding I. Compounds: Definition: Properties of compounds: Compounds can be decomposed (separated) only by chemical means (not physical).

Chemical Bonds Force between 2 atoms Three bond types: ________________________

Electronegativity Ability of an atom in a compound to attract electrons from another atom. Difference between electronegativity of atoms is used to determine the bond type.

Periodic Table with Electronegativities H He 3 Li Be B C N O F Ne 11 Na Mg Al Si P S Cl Ar 19 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf 105 Ha 106 Sg 107 Ns 10 8 Hs 10 9 Mt 11 0 Uu n 111 Uu u 112 Uu b Electronegativity Values for Elements Circle elements with highest & lowest value & label. Show trends for EN using arrows.

Electronegativity Differences Electronegativity Differences = ∆EN O 3.2

Determining bond type Determine the absolute difference (either + or -) Type? O ___ - N____= _____ O ___ - O____=_____ O ___ - H____=_____ F____- Li ____=_____ ElementEN F4.0 (4.1) 03.5 N3.1 H2.1 Li1.0 Be1.5

Electronegativity Learning Guide Determine absolute differences Classify each bonding pair of elements as: Ionic Covalent If covalent, determine if the bond is: non-polar (∆ 0 – 0.3) or polar (∆0.4 – 1.7)

Ionic Bond ∆EN = 1.8 – 3.2

Types of Bonds Ionic Covalent Metallic

Ionic Bond Ionic Bond: formed with Bonds a __________ with a ____________ Valence electrons are ________________ from the ___________ to the __________. Therefore, when the valence electron(s) are transferred to the ____-______, the NM become _______ charged (a ________).

Ionic bonds The electronegativity difference must be equal to or greater than __________. Ionic bonds look like: Na Cl

Opposite charges attract= electrostatic attraction Formula unit Like the attraction of magnets

Ionic compounds Ionic bonds form ionic compounds. An ionic compound is composed of positive (cations) and negative (anions) ions that are combined so that the negative and positive charges are equal.

Why do some atoms in formulas have subscripts and others do not?

Ionic Formula Ionic formula units: The charges of the atoms in the compound must equal to zero. Na ion (Na ) and Cl ion (Cl ) _______ + ________ = 0 Na ion (Na ) and Ca ion (Ca ) _______ + ________ = 0

Ionic compound names Metal name + Non-metal (ide) Prefix?? Note: will practice names & formulas after determining bonds

Opposites Attract Find ions that can bond Write the symbol and the charge Write the new compound formed by combining the ions. Name the compound. Write at least 15 compounds. At least 10 should include subscripts.

Video: Discovery Ed Ionic bonds

Covalent Bond Non-metal and Non-metal Sharing of electrons to form a bond

Covalent Bonds Bonds a ___________ to a ___________. Valence electrons are __________ between a _________ and a _________.

Electronegativity Difference The electronegativity difference must be equal to or less than _______. It is a polar covalent bond if the difference is between __________. It is a non-polar covalent bond if the difference is between ___________.

Non-Polar Covalent Bond ∆EN= 0 – 0.3 The Electron pair that makes up the bond is shared evenly.

Non-Polar Covalent Bond

Polar Covalent Bond

Polar Covalent Bond ∆EN = 0.4 – 1.7 The electron pair that makes up the bond is closer to the element that has the higher electronegativity.

Polar Covalent Bond

Covalent Bonds Covalent bonds form covalent compounds, also called molecular compounds or molecules. WaterHydrogen Polarity: unequal distribution of charges One side: more negative, The other side: more positive

Video: Discovery Ed – covalent bonds Elements of chemistry: Compounds & Reactions

Metallic Bond Metal to Metal Electrons flow freely

Metallic Bonds Bonds a _________ to a ____________. The valence electrons ________ ______ and are not bonded to one atom. The valence electrons from a ______ of ________.

Metallic bond: Sea of electrons The freedom of movement of the electrons in network of metals gives characteristic metallic properties: -

Bond type Compound (names & formulas) Properties (physical and chemical)

Review Metals __________ electrons because they have ________ electronegativity (EN) Non-metals ________ electrons and have ________ electronegativity.

Warm-up: What type of bonds are created with: Ionic, Covalent (non-polar or polar) Use the PT (but not the electronegativity chart) Cr and Fe Rb and Br Cl and Cl H and F Ba and I S and S

Covalent Bonds – Strength What is the Relationship between: -Bond energy & Bond length -Bond energy & Number of bonds

Intermolecular forces What holds the separate covalent bonds together?

Lewis structures: A different way Practice Lewis structures (electron dot) Structural formula (shows bonds with lines) Introduce shape of compounds VSEPR Determine polarity Identify diatomic molecules (7)

Electronic cereal: Start with diatomic molecules 2 atoms of the same element (7) Rules to follow: Make every compound 1. Use different colors for each atom 2. Show how each atom contributes electrons to the bond and the lone pairs 3. Determine shape & polarity 1. Polarity is?

Electronic Cereal: F ₂

Working with Moles Peer Tutoring: Working in pairs

Mole Flow Chart Mole

Mole Conversions (Factor Label Method) Moles ↔ Grams Molar mass: 1 mole of = ? Grams

Moles ↔ Particles (atoms, molecules, compounds, etc.) 1 mole = atoms Review scientific notation

Moles ↔ Volume of Gas (at STP) 1 mole of a gas = Liters

What I know:Show work What I need to know: Formula for conversionAnswer with correct units: Analyze the problem:

What I know:Show work What I need to know: Formula for conversionAnswer with correct units: 1. How many moles are in 100 Liters of Rn?

What I know:Show work What I need to know: Formula for conversionAnswer with correct units: #4 How many atoms are in 3.5 moles of Xe?

What I know:Show work What I need to know: Formula for conversionAnswer with correct units: #6 How many grams are in 3.75 moles of Kr?

Bond types determines properties of the compounds Graphic organizer

Properties of Ionic Compounds

Properties of Covalent Compounds (molecules) StructureGas, Liquid or “soft” solid HardnessLow Melting pointLow to medium Boiling PointLow to medium Electrical conductivityNo Soluble in waterOnly if polar covalent compound

Properties of Metallic Solids StructureSolid HardnessMedium (malleable, ductile) Melting pointMedium to high Boiling pointMedium to high Electrical conductivityYes Soluble in waterNo

Ionic Bond

Ionic Compounds- Formulas

Opposites Attract Find ions that can bond Write the symbol and the charge Write the new compound formed by combining the ions. Name the compound. Write at least 15 compounds. Ten should include subscripts.

Ionic Compounds Names and Formulas Binary With Transition metals With Polyatomic ions (Tertiary)

Transition metals can have more than one charge

Covalent Compounds Names and Formulas Review: Binary

Names & Formulas Diatomic molecules Acids

Bond type Compound (names & formulas) Properties (physical and chemical)

Foldable – Front cover Covalent Bonds form Molecules (Covalent compounds) Ionic Bonds form Ionic Compounds Metallic Bonds form Metallic Solids

Page 1 Covalent bond Picture Ionic bond Picture Metallic bond Picture Type of atoms Electrons are: EN difference Type of atoms Electrons are: EN difference Type of atoms Electrons are:

Page 2 Molecules (covalent compounds) Lewis structure of water Ionic Compounds (salts) Picture Metallic solid Properties of molecules Properties of Ionic compounds Properties of metallic solids

Page 3 Common examples of molecules Common examples of ionic compounds Common examples of metallic solids Names & formulas - Binary molecules - Binary ionic compounds - Brass - Pewter - Sterling silver - Stainless steel

Page 4 – names & formulas Molecules Diatomic molecules Acids Ionic Compounds Transition metals Polyatomic ions Metallic solids Bronze Gold

Lewis Diagrams Count and add the valence electrons for each atom. Put C as the central atom (or element with with lowest electronegativity). Hydrogen is never the central atom Place 2 electrons for each bond between 2 atoms. Arrange the other electrons evenly around the atoms to satisfy the octet rule. Duet rule for H. If there are not enough electrons, make double or triple bonds.

Lewis Diagrams Valence Shell Electron Pair Repulsion VSEPR This means:

Ionic Bond