4/12 Bell Work Nothing is particularly hard if you divide it into small jobs. -- Henry Ford Who is Henry Ford, and what did he mean?

4/12 Schedule Finish Tests if needed Use notes, Periodic Table, calculator, snake chart, and Review sheet Notes online “Chemical Formulas and Compounds” Ch 6.1 “Compounds and Molecules” Assignments: 1. Concept Review Ch 6 “Compounds” - TBA

Unit : Chemical Formulas & Compounds Ch 6 Objectives: Correctly name and write formulas for compounds. Compare/contrast different bond types.

Ch 6.1 “Compounds and Molecules” Objectives Describe chemical bonds. Model compound structure in different ways. Explain what causes compound properties.

Chemical Structure Intro Study the models of the water molecule, H2O, and the carbon dioxide molecule, CO2. 1. Name some similarities between the molecules of H2O and CO2. 2. How are the molecules different?

Chemical Bonds Bonds Compounds have very specific formulas Hold atoms or ions together in compounds Compounds have very specific formulas H20 (water) and H2O2 (peroxide) have very different properties.

Chemical Structure Multiple Structure Models Chemical Structure: the arrangement of atoms in a substance Some models represent bond lengths and angles. bond length: the average distance between the nuclei of two bonded atoms bond angle: the angle formed by two bonds to the same atom, shows the shape of the compound

Bond Length Model Ball and Stick Model Space filled model

Chemical Structure Ball-and-stick model, Atoms are balls. Bonds holding atoms together are sticks. Structural formulas Chemical symbols represent atoms. Space-filling models Show the space occupied by atoms.

Chemical Structure Flexible Bonds bend, stretch, and rotate without breaking. Could be represented by flexible springs. Most reported bond lengths are average distances. There are different kinds of bonds All atoms are vibrating because of thermal energy

Structure Affects Properties? The chemical structure of a compound determines its properties.

Structure Affects Properties? Network structures make strong solids. Example: Quartz, SiO2 is made of silicon and oxygen atoms. The atoms are bonded in a strong, rigid structure (aka crystals). Titanium flame aura quartz

Structure Affects Properties? Ionic Networks The strong attractions between the oppositely charged ions gives these compounds high melting points and high boiling points. EX: Table salt—sodium chloride—is a tightly packed repeating network of positive Na+ ions and Cl- ions.

Structure Affects Properties? Sodium chloride Melting point: 801o C or 1474o F Boiling point: 1413o C or 2575o F Sodium chloride crystal

Structure Affects Properties? Some compounds are molecules. Can be solids, liquids, or gases. The strength of attractions between molecules varies. High melting and boiling points = strong attractions Low mp and bp = weak attractions

Structure Affects Properties? Sucrose (table sugar) Melting point: breaks down at 186o C Boiling point: NA Sucrose crystal

Water Bonding Hydrogen Bonding H is attracted to O, N, and F EX: Water. Not as strong as the bonds holding the molecule together.

4/13 Bell Work Solve the word puzzles. Working overtime, do without, teddy bear

4/13 Schedule Compound Properties Lab Work Notes Ch 6.1 “Compounds and Molecules” Concept Review Ch 6 “Compounds” Assignments: 1. Concept Review Ch 6 “Compounds” - TBA

Chemical Models Review Identify which model of methane is the: Ball-and-stick model Structural formulas Space-filling models

Bunsen Burner Procedure Inspect burner and tubing for rust or cracks. Close air hole on burner and attach tubing to gas jet. Turn gas on until you hear a faint hiss. Quickly use striker to light burner. If it doesn’t light in 2-3 tries, turn off gas and wait for it to dissipate before trying again. Adjust flame as needed using the metal sleeve, usually looking for a double cone of blue flame. Turn off gas and carefully disconnect tubing.

Compound Properties Lab WEAR. YOUR. GOGGLES!! Be careful… hot! Read the lab carefully! Refer Ch 6.1 “Compounds and Molecules” book/notes and lab to answer questions. Clean Up Foil and used chemicals in lab garbage. Disconnect Bunsen burners. Materials back where you found them.

4/18 Bell Work A railroad line has a double track, except in a tunnel where there isn’t enough room. A train goes in the tunnel in one direction. Another train enters in the opposite direction. Both trains are traveling very fast, yet they do not collide. How can this be? Enter at different times

4/18 Schedule Notes Ch 6.2 “Ionic and Covalent Bonding” Work Concept Review Ch 6 “Compounds” Finish Compound Properties Lab - TODAY Assignments: 1. Concept Review Ch 6 “Compounds” - TBA

Ch 6.2 “Ionic and Covalent Bonding” Objectives Explain why atoms form bonds. Compare and contrast ionic, covalent, and metallic bonds. Describe how polyatomic ions are similar to other ions.

DTC: “Chemical Bonds” Watch the video clip as Paige and Dexter demonstrate how chemical bonds are formed. Be able to answer the questions below. In ionic bonds, electrons are __________________. What is the difference between an anion and a cation? Valence electrons are _____________ in covalent bonds.

Bonding Preview An ionic bond is a chemical bond that is usually formed between a metal and a nonmetal. In an ionic bond, electrons are gained or lost. A covalent bond is a bond that is usually formed between two nonmetals. These atoms share electrons.

Bonding Preview What kind of bond would join two oxygen atoms? What kind of bond would join sodium atoms with chlorine atoms to form salt? What kind of bond would join a hydrogen atom with an oxygen atom?

Why Do Chemical Bonds Form? Bonding Rationale and Type Generally, atoms join so each has a stable electron configuration. “Noble gas envy” Usually 8 electrons 2 basic kinds of chemical bonding: ionic bonding covalent bonding

Comparing Ionic and Covalent Bonds

Ionic Bonds Ionic bonds are formed by the transfer of electrons. Atoms tend to form ionic bonds when one atom has more attraction for electrons than the other. Made of ions or metal and a nonmetal Ionic compounds form of networks. A formula unit is the smallest ratio of ions in ionic compounds.

Ionic Bonds

Ionic Bonds This is a calcium fluoride crystal. Use the formula unit to predict how to write its chemical formula.

Polyatomic Ions Polyatomic Ions: an ion made of two or more atoms Function and travel as a unit Common examples hydroxide – OH- carbonate -- CO3 2- ammonium – NH4 + Use parenthesis if you need to write more than 1 Ex: the formula for ammonium sulfate is written as (NH4)2SO4, not N2H8SO4.

Polyatomic Ions Usually names of polyatomic anions relate to their oxygen content. An -ate ending names the ion with more oxygen atoms. Examples: sulfate (SO42–), nitrate (NO3–), chlorate (ClO3–) An -ite ending names the ion with fewer oxygen atoms. Examples: sulfite (SO32–), nitrite (NO2–), chlorite (ClO2–)

Polyatomic Ions

Covalent Bonds Covalent bonds share… covalent bond: a bond formed when atoms share one or more pairs of electrons. Networks of bonded atoms, such as silicon dioxide, are also covalently bonded. Usually form between nonmetal atoms Common covalent compounds: water, sugar, and nitrous oxide.

Covalent Bonds Covalent compounds can be solids, liquids, or gases. In a chlorine molecule, Cl2, the atoms share two electrons. One pair = single covalent bond. 5th stopped here

Covalent Bonds Atoms may share more than one pair of electrons. Two pairs form a double covalent bond. 4 electrons Stronger and shorter than single bonds aka double bonds Three pairs of shared electrons form a triple covalent bond. 6 electrons Stronger and shorter than double bonds

Multiple Bonds

4/19 Bell Work How many numbers between 1-100 are multiples both of 2 and 3? 16 33 multiples of 3, half are even

4/19 Schedule Notes Ch 6.2 “Ionic and Covalent Bonding” Lewis Structure Wksht due FRIDAY Work Concept Review Ch 6 “Compounds” Finish Compound Properties Lab - LATE Assignments: Concept Review Ch 6 “Compounds” – TBA Compound Properties Lab – LATE Lewis Structure Wksht - FRIDAY

Predicting Bonds: Lewis Structures Lewis Structures predict how atoms are connected in compounds. Find your element on the periodic table. Determine the number of valence electrons. This is how many electrons you will draw.

Groups - Review Group 1 = 1 electron Group 8 = 8 electrons Except for He, it has 2 electrons Group 2 = 2 electrons 3, 4, 5, 6, 7 The electrons in the outer shell are called “valence electrons” www.chem4kids.com

Lewis Structures Find out which group your element is in. This tells you the number of valence electrons. www.chem4kids.com

C Lewis Structures Write the element symbol. Carbon is in the 4th group, so it has 4 valence electrons. Starting at the right, draw 4 electron dots, counter- clockwise around the element symbol. Only pair up if there are more than 4. C

Lewis Structures Try these elements on your own. H P Ca Ar Cl Al C

Lewis Structures of Compounds Figuring out Structure of Compounds The goal of the Lewis structure is to have all atoms stable (usually 8). Exceptions: H only wants 2 e-,B wants 6, P can have 10, S can have 12 Write the chemical formula, and count the total # of valence electrons. This is the amount of electrons allowed in the Lewis Structure These electrons can be placed anywhere in the structure and don’t belong to any specific atom.

Lewis Structures of Compounds Figuring out Structure of Compounds Arrange the atoms around each other, sharing electrons as needed Put the dot structure in brackets and include charge if it is a polyatomic ion. Water vs Hydroxide ion

Lewis Structures of Compounds Hints: a) The least electronegative atom typically goes in the center - usually C b) Hydrogen is terminal (at the end b/c it only can form 1 bond) 3. Put in electrons (dots) around the atoms to satisfy the octet of atoms 4. Check to see that you have the same # e-s as in step 1, if not, rearrange the # e-s and/or atoms.

Lewis Structure Examples H2O CCl4 BI3

4/20 Bell Work Two hours ago it was as long after 1 o’clock in the afternoon as it was before 1 o’clock in the morning. What time is it now? 9 o’clock, 1+6 = 7+2 = 9

4/20 Schedule Notes Ch 6.2 Review Lewis Structures Work Concept Review Ch 6 “Compounds” Finish Compound Properties Lab – LATE Lewis Structure Wksht due FRIDAY Assignments: Concept Review Ch 6 “Compounds” – TBA Compound Properties Lab – LATE Lewis Structure Wksht - FRIDAY

Covalent Bonds Atoms do not always share electrons equally. Nonpolar covalent bonds: electrons are shared equally Polar covalent bond: unequal sharing of electrons. Coordinate covalent bonds: both shared electrons come from one element Electrons tend to be more attracted to atoms farther to the right and closer to the top of the periodic table. Fl most, Fr least

Metallic Bonds Distinctive Metal Properties Metals are flexible and conduct electricity because their atoms and electrons can move freely throughout a metal’s packed structure. metallic bond: a bond formed by the attraction between positively charged metal ions and the electrons around them Metal cations in a “sea” of electrons.

Review Lewis Structures ClO31- (expanded octet or coordinate covalent) Number e- = Brackets and charge? HCN (multiple bonds) ClF3 (expanded octet)