Metallic & Ionic Bonding Test Date: Thurs, Feb 18

conductive malleable ductile Properties: Metallic Bonds Properties: electricity flows through them: __________ can be hammered into sheets: _______ can be drawn into a wire: _______ conductive malleable ductile

Delocalized electrons Electrons do not belong to any one atom Metallic Bonding Attraction of a metallic cation (+ ion) and valence electrons that are free to move (delocalized) Delocalized electrons Electrons do not belong to any one atom Sometimes called a “sea of electrons”

Metallic bond = a positive core surrounded by a “sea” of electrons

Properties of Ionic Compounds Most form solid crystals (called “salts”) at room temperature Have High melting points (strength of electrostatic attraction) Form electrolytes (ions in solution) which can conduct electricity when dissolved in water (aqueous). When dissolved the electrons are permitted to move freely (compare to ionic compound crystal structure)

Ionic vs Metallic = + + =

Ions are surrounded by ions of opposite charge. A crystal lattice is formed.

loses positive cation gains negative anion Ionic Bonding Involves the transfer of electron(s) from a metal to a nonmetal. The metal _____ electrons becoming ________ and is called a _______. The non-metal _____ electrons becoming _______ and is called an _______. loses positive cation gains negative anion

Electrostatic Interactions “Opposites attract” Cations and anions are attracted to each other through strong electrostatic attractions – stronger than metallic bonds The result is a stable, low energy ionic compound Ionic compounds are neutral since the charges of the cation and anion cancel

Valence Electron Dot Structures for Ionic Compounds Example 1: Na & Cl Determine the number of valence electrons for each element From the valence count, draw the Lewis valence electron dot structures of Na and Cl Show how the electron is transferred from Na to Cl to form ions

So what IS an ionic bond? Ionic compounds do not actually bond. Electrons are completely gained or lost (transferred), NOT shared!!!! The electrostatic attraction is the ionic “bond.”

Valence Electron Dot Structures for Ionic Compounds Example 2: Mg & O Example 3: Ca & Cl

Why do atoms gain or lose electrons? more stable In order to become _________ What makes something stable? It is lower in energy It has a full valence shell It’s electron configuration is the same as a _________ ________ noble gas

Every atom wants to be like a noble! Stability: Atom vs. Ion Which is more stable, Na or Na+1? Every atom wants to be like a noble!

Electronegativity in Ionic Bonds What does electronegativity mean? Attraction for valence electrons in a bond What element is the MOST electronegative? Fluorine (F) What element is the LEAST electronegative? Francium (Fr)

Electronegativity in Ionic Bonds The larger the difference between the EN values in a compound, the stronger the ionic bond. What compound would have the STRONGEST ionic bond that is possible? FrF I’m strong; does that mean I’m ionic?

Electronegativity Values

What is a formula unit? One single unit of the ionic compound Smallest ratio of cations to anions that form an electrically neutral compound Ex. NaCl vs. MgCl2

Common Polyatomic Ions Ammonium Acetate Carbonate Hydroxide Nitrate Nitrite Permanganate Phosphate Sulfate Sulfite (NH4)+1 (C2H3O2)-1 (CO3)-2 (OH)-1 (NO3)-1 (NO2)-1 (MnO4)-1 (PO4)-3 (SO4)-2 (SO3)-2

How does the charge work? Ignore the subscripts and treat the group as one thing: (NO3) -1 total charge is -1 (SO4) -2 total charge is -2 (PO4) -3 total charge is -3

Write the formula for these compounds: 1. Ca2+ + (NO3) 2. Cr 4+ + Cl- 3. NH4 + O2- 4. Cu2+ + S2- 5. Ni2+ + N3- 6. Ag+ + O2- Ca(NO3)2 CrCl4 (NH4)2O CuS Ni3N2 Ag2O

Ionic Bonding Recap Questions Copy the question and answer in complete sentences What is the total charge on an ionic compound? What holds the anions to the cations? In other words, how is an ionic “bond” formed? List the pair(s) of elements below that are likely to form ionic compounds? Remember that ionic compounds are formed between metals and nonmetals. Write the balanced formula. Cl, Br Li, Cl K, He I, Na What properties characterize ionic compounds? Why do ionic compounds conduct electricity when they are melted or dissolved in water? What is a formula unit? What does it represent?

Covalent Bonding

Ionic Compound Properties (Review) Exhibit a crystal structure Exist as solids Dissolve easily in water Have high melting and boiling points Conduct electricity in solutions Have high electronegativity differences

Covalent Compound Properties Properties of Covalent Compounds… Have low melting and boiling points Do not dissolve easily in water Do not conduct electricity in solutions Exist as gases, liquids, or solids Have low electronegativity differences

Common Covalent Compounds Nitrous oxide (N2O) is laughing gas used as an anesthetic and to boost auto engine power Methane (CH4) is a flammable gas used as fuel and in homes for domestic heating and cooking purposes. Sugars, like sucrose (C12H22O11) and glucose (C6H12O6), are used in food and energy production Hydrogen peroxide (H2O2) is used as a bleaching agent, emetic (induces vomiting), and an antiseptic (clean cuts and scrapes)

Common Covalent Compounds Carbon dioxide (CO2) is a gas used by plants during photosynthesis, produced in respiration; it is a byproduct of burning fossil fuels, and it has many uses as a fire extinguisher, refrigerant (dry ice), and carbonation in drinks

Common Covalent Compounds Water (H2O) is a liquid that is vital for life. It covers about 71% of earth’s surface, and makes up about 60% of the human body. It is known as the universal solvent, and has many unique properties and uses.

Diatomic Elements Some nonmetal elements on the periodic table exist in nature only as pairs called diatomic molecules; bonded covalently H, O, F, Br, I, N, Cl Hydrogen Molecule (H2) http://web.jjay.cuny.edu/~acarpi/NSC/5-bonds.htm

Covalent Bonds Occurs when valence electrons are shared between atoms – usually between nonmetallic elements Covalently bonded compound known as a molecule These shared electrons are part of the valences of all atoms involved (satisfies octet rule) Since electrons are shared, no charges appear Many combinations can occur between two nonmetals Example: carbon and oxygen can form carbon monoxide (CO) and carbon dioxide (CO2) Carbon Dioxide

Rules for Lewis Structures 1. Make certain that the bond is a covalent bond by checking the electronegativity difference. Then set up the skeleton structure as follows: The atom with the lowest electronegativity will tend to go in middle Place all the other atoms around this central atom Attach these atoms to the central atom in reasonable fashion with single bonds

Rules for Lewis Structures 2. Sum valence electrons 3. Complete octets of peripheral atoms 4. Place leftover e- on central atom 5. If necessary use multiple bonds to fill the center atom's octet.

Write the structural formulas for: Cl2 NH3 CH4 H2O

Polyatomic Ions (K ONLY) Draw the electron dot structures for: CO32- NO3- SO32- SO42-

Single Covalent Bonds Ex: Methane (CH4) Atoms of some elements attain a noble gas configuration by sharing one pair of electrons between two atoms When drawing these molecules, a line can represent a pair of shared electrons Ex: Methane (CH4)

Multiple Covalent Bonds Sometimes, atoms share more than one pair of electrons between two atoms When drawing these molecules, multiple lines can represent pairs of shared electrons Ex: diatomic oxygen (O2) and nitrogen (N2) How many pairs of electrons does each kind of bond share? Single: _________ Double: _________ Triple: _________ 1 pair 2 pairs 3 pairs

Draw the electron dot structures for the following CO2 C2H4 NO2 SO2 CS2

Exceptions to Octet Rule Beryllium Has 2 valence electrons Full with 4 valence electrons Ex: BeI2 Aluminum 3 valence electrons Full with 6 valence electrons Ex: AlCl3 Boron Ex: BH3

Exceptions to Octet Rule Cont’d Expanded octets Some atoms bond so they have more than 8 electrons in their valence Occurs only around a central nonmetallic atom from period 3 or higher (most commonly sulfur & phosphorous) Ex: PCl5 and SF6 Trigonal Bipyramidal Octahedral

Polar & Nonpolar Covalent Bonds Covalent bonds share electrons equally and unequally (“tug of war” with electrons) Which molecule appears “balanced”? Which one does not? H2O O2 Water (H2O) Oxygen (O2)

Polar Covalent Bonds Unequal sharing of electrons Occurs when atoms that share electrons have different electronegativities Shared electrons spend a greater amount of time at the more electronegative atom Example: water (H2O)

Nonpolar Covalent Bonds Equal sharing of electrons Occurs in two scenarios… No difference in electronegativity between atoms that are sharing (diatomic molecules) Example: chlorine (Cl2) Shape of molecule pulls electrons equally in all directions Example: methane (CH4) Is this even correct?

Bonding & Electronegativity Atoms bond according to the difference in their electronegativities Look at table of EN values and find the difference between the two atoms involved (absolute value) If EN difference is… < 0.5 = nonpolar covalent bond 0.5 – 1.7 = polar covalent bond >1.7 = ionic bond <0.5 0.5--1.7

Bonding & Electronegativity

Bonding & Electronegativity Try to predict the bond type (ionic, polar covalent, nonpolar covalent) using your EN table: Formula EN values EN Difference Bond Type LiCl Li = 1.0 Cl = 3.0 2.0 ionic bonds PCl3 MgO CH4 NF3 P = 2.1 Cl = 3.0 0.9 polar covalent bonds Mg = 1.2 O = 3.5 2.3 ionic bonds C = 2.5 H = 2.1 0.4 nonpolar covalent bonds N = 3.0 F = 4.0 1.0 polar covalent bonds

Molecular Shapes 2 linear 180° 3 trigonal planar 120° 1 bent <120° # of Electron Groups Number of Lone Pairs Electron Pair Arrangement Molecular Geometry Approximate Bond Angles 2 linear 180°   3 trigonal planar 120° 1 bent <120° 4 tetrahedral 109.5° trigonal pyramid <109.5° (~107°) <109.5°(~105°)

Molecular Shape Try to predict the shape using VSEPR and your shape chart: 1) BCl3 2) CH4 3) NH3 Lewis Dot Central Atom # e- pairs # bonded pairs # lone pairs Shape

Molecular Shape Example: What is the shape of water (H2O)? 1) Central atom? oxygen 2) Draw Lewis Dot… 3) # of total electron pairs around central atom? 4 4) # of bonding pairs around central atom? 2 5) # of lone pairs around central atom? 2 6) Refer to chart to identify shape…angular (bent)

Molecular Shapes Applies to covalent compounds only. Use VSEPR steps (valence shell electron pair repulsion): 1) Identify the central atom as the element that can form the most bonds 2) Draw the Lewis dot structure for the molecule 3) Count total # of electron pairs around the central atom 4) Count # of bonding pairs of electrons around the central atom 5) Count # of lone pairs of electrons around the central atom 6) Look at summary chart, identify shape

Polar & Nonpolar Molecules Polar molecules have a partial positive and partial negative charge – called a dipole Dependent upon location and nature of the covalent bonds they contain Molecules are considered polar if they: Have a polar covalent bond - EN difference between 0.5 - 1.7 Have an asymmetrical shape - trigonal pyramidal - linear (with 2 different elements) - angular (bent) If both criteria are not met, it is either a nonpolar molecule or an ionic compound

Polar & Nonpolar Molecules *IMPORTANT: Polar & nonpolar molecules are different from polar & nonpolar bonds!!! Non-polar molecules have charges that are evenly distributed, due to shape (ex: any diatomic molecule, gasoline) Polar molecules have a partial positive and a partial negative charge (ex: water)

Polar & Nonpolar Molecules Evaluate and identify each molecule as polar covalent or nonpolar covalent: Formula Has a polar covalent bond Has an asymmetrical shape Identity H2O  polar molecule CH4 BCl3 HCl x nonpolar molecule nonpolar molecule x  polar molecule 

Property Ionic Bonds Covalent Bonds Electrons are: Transferred Shared Difference in Electronegativity: <0.5 nonpolar 0.5 to 1.7 polar >1.7 A metal and nonmetal Bond between: 2 nonmetals State at room temperature Solid Solid, Liquid, or Gas Particle Name: Formula Unit Molecule High Low Melting Point: Conducts Electricity? Yes No Dissolves in water? Yes No (usually) Yes No Flammable Forms a more stable configuration? Yes Yes Examples: NaCl, MgI2 NH3, CHCl3

Types of Multiple Bonds Sigma Bond: covalent chemical bond where ends of orbitals overlap; present in single and multiple bonds Pi Bond: covalent chemical bond where parallel orbitals overlap to share electrons; only present in multiple bonds Type of Bond Sigma Bonds Pi Bonds Single 1 Double Triple 2

Orbital Hybridization - Boron

Orbital Hybridization Orbital Hybridization: 2 or more different types of orbitals (usually s, p, or d) mix to become the same number of identical orbitals around the central atom 2 bonds sp hybridization 2 equivalent orbitals 3 bonds sp2 hybridization 3 equivalent orbitals 4 bonds sp3 hybridization 4 equivalent orbitals 5 bonds sp3d hybridization 5 equivalent orbitals 6 bonds sp3d2 hybridization 6 equivalent orbitals *Lone pairs and sigma bonds count as equivalent orbitals

Orbital Hybridization - Carbon