Chapter 12 Lecture Conceptual Integrated Science Second Edition © 2013 Pearson Education, Inc. Chemical Bonds and Mixtures

© 2013 Pearson Education, Inc. This lecture will help you understand: Electron-Dot Structures The Formation of Ions Ionic Bonds Metallic Bonds Covalent Bonds Polar Covalent Bonds Molecular Polarity Molecular Attractions Most Materials Are Mixtures The Chemist's Classification of Matter Solutions Solubility

© 2013 Pearson Education, Inc. Electron-Dot Structures Atoms bond together through their electrons. To learn about bonding, therefore, we need to know something about how the electrons in an atom are organized. Electrons behave as though they are contained within seven concentric shells.

© 2013 Pearson Education, Inc. Electron-Dot Structures The numbers indicate the maximum number of electrons each shell may contain. Note: This is a "conceptual model" and not a representation of what an atom "looks like." Rather, it helps us to understand how the electrons in atoms behave.

© 2013 Pearson Education, Inc. Electron-Dot Structures The shells are more easily drawn in two dimensions. Each atom has its own configuration of electrons. Elements in the same group have similar configurations, which is why they have similar properties.

© 2013 Pearson Education, Inc. Electron-Dot Structures Valence electrons are electrons in the outermost shell of an atom. These are the ones that can participate in chemical bonding. An electron-dot structure is a notation that shows the valence electrons surrounding the atomic symbol.

© 2013 Pearson Education, Inc. Kr Electron-Dot Structures Special Note –For heavier atoms, some valence electrons are more available than others. Krypton, for example, has 18 valence electrons, but only eight of these are typically shown in an electron-dot structure. These are the eight that extend farthest away from the nucleus.

© 2013 Pearson Education, Inc. Electron-Dot Structures Note that elements in the same group have the same electron-dot structure.

© 2013 Pearson Education, Inc. Electron-Dot Structures CHECK YOUR NEIGHBOR Sodium, Na, atomic number 11, has only one valence electron. Upon losing this electron, what other atom in the periodic table does the sodium resemble? A.neon, Ne, atomic number 10 B.magnesium, Mg, atomic number 12 C.lithium, Li, atomic number 3 D.Sodium can resemble only sodium. Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. Electron-Dot Structures CHECK YOUR ANSWER Sodium, Na, atomic number 11, has only one valence electron. Upon losing this electron, what other atom in the periodic table does the sodium resemble? A.neon, Ne, atomic number 10 B.magnesium, Mg, atomic number 12 C.lithium, Li, atomic number 3 D.Sodium can resemble only sodium. Explanation: With 10 electrons, the sodium has enough electrons to fill the first and second shells, just like neon, Ne.

© 2013 Pearson Education, Inc. The Formation of Ions An ion is an atom that has lost or gained one or more electrons.

© 2013 Pearson Education, Inc. The Formation of Ions

© 2013 Pearson Education, Inc. H O H H+H+ WaterHydrogen ion H O H H + Hydronium ion, H 3 O + The Formation of Ions A molecular ion is typically formed by the loss or gain of a hydrogen ion, H +.

© 2013 Pearson Education, Inc. Na + F-F- Ionic Bonds An ionic bond is the electrical force of attraction between oppositely charged ions.

© 2013 Pearson Education, Inc. Ionic Bonds CHECK YOUR NEIGHBOR What is the chemical formula for a compound made of aluminum ions, Al 3+, and oxygen ions, O 2– ? A.AlO B.Al 3 O 2 C.Al 2 O 3 D.Al 6 O 6 Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. Ionic Bonds CHECK YOUR ANSWER What is the chemical formula for a compound made of aluminum ions, Al 3+, and oxygen ions, O 2– ? A.AlO B.Al 3 O 2 C.Al 2 O 3 D.Al 6 O 6

© 2013 Pearson Education, Inc. Ionic Bonds CHECK YOUR NEIGHBOR What is the chemical formula for a compound made of magnesium ions, Mg 2+, and oxygen ions, O 2– ? A.MgO B.Mg 2 O 2 C.Mg 4 O 4 D.any of the above Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. Ionic Bonds CHECK YOUR ANSWER What is the chemical formula for a compound made of magnesium ions, Mg 2+, and oxygen ions, O 2– ? A.MgO B.Mg 2 O 2 C.Mg 4 O 4 D.any of the above Explanation: The chemical formula is used to show the ratio in which atoms combine. By convention, the lowest numbers are preferred, so 1:1 is used rather than 2:2. The numeral 1, however, is implied when no subscript is written.

© 2013 Pearson Education, Inc. Metallic Bonds Outer electrons in metal atoms are held only weakly by the nucleus. This weak attraction allows the electrons to move about quite freely. This mobility of electrons accounts for many metallic properties.

© 2013 Pearson Education, Inc. Metallic Bonds An alloy is a mixture of metallic elements.

© 2013 Pearson Education, Inc. Covalent Bonds A covalent bond is the type of electrical attraction in which atoms are held together by their mutual attraction for shared electrons.

© 2013 Pearson Education, Inc. F — FF Covalent Bonds There are two electrons in a single covalent bond. The covalent bond is represented using a straight line.

© 2013 Pearson Education, Inc. Covalent Bonds The number of covalent bonds an atom can form equals its number of unpaired valence electrons.

© 2013 Pearson Education, Inc. Covalent Bonds

© 2013 Pearson Education, Inc. Covalent Bonds Multiple covalent bonds are possible.

© 2013 Pearson Education, Inc. Polar Covalent Bonds Electrons in a covalent bond are shared evenly when the two atoms are the same.

© 2013 Pearson Education, Inc. Polar Covalent Bonds Electrons in a covalent bond may be shared unevenly, however, when the bonded atoms are different.

© 2013 Pearson Education, Inc. High Low Polar Covalent Bonds Electronegativity is the ability of a bonded atom to pull on shared electrons. Greater electronegativity means greater "pulling power."

© 2013 Pearson Education, Inc. Polar Covalent Bonds

© 2013 Pearson Education, Inc. Polar Covalent Bonds CHECK YOUR NEIGHBOR Which is heavier: carbon dioxide, CO 2, or water, H 2 O? A.Carbon dioxide is heavier. B.Water is heavier. C.Both have the same number of atoms, so they weigh the same. D.It depends on other factors. Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. Polar Covalent Bonds CHECK YOUR ANSWER Which is heavier: carbon dioxide, CO 2, or water, H 2 O? A.Carbon dioxide is heavier. B.Water is heavier. C.Both have the same number of atoms, so they weigh the same. D.It depends on other factors. Explanation: Look to the periodic table and add up the masses of the atoms in each of these substances. Carbon dioxide adds up to 44 amu, while water is only 18 amu. So, carbon dioxide is more than twice as heavy. At room temperature, carbon dioxide is a gas because it is nonpolar.

© 2013 Pearson Education, Inc. Molecular Polarity If the polar bonds in a molecule are facing in equal and opposite directions, the polarity may cancel out.

© 2013 Pearson Education, Inc. Molecular Polarity …Or not!

© 2013 Pearson Education, Inc. Molecular Polarity

© 2013 Pearson Education, Inc. Molecular Polarity CHECK YOUR NEIGHBOR Water has such a relatively high boiling point because water A.is such a heavy substance. B.is transparent so that heat passes right through it. C.contains three atoms per molecule. D.molecules are so sticky. Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. Molecular Polarity CHECK YOUR ANSWER Water has such a relatively high boiling point because water A.is such a heavy substance. B.is transparent so that heat passes right through it. C.contains three atoms per molecule. D.molecules are so sticky. Explanation: The slightly negative end of one water molecule holds onto the slightly positive end of another water molecule. This force of attraction must be overcome before the liquid water can transform into the gaseous phase.

© 2013 Pearson Education, Inc. Na + Cl - H O H H O H H O H O H H O H H H H O Molecular Attractions An ion dipole attraction is the attraction between an ion and a dipole. –Example: NaCl in water

© 2013 Pearson Education, Inc. Molecular Attractions An dipole-dipole attraction is the attraction between two dipoles. –Example: cohesive forces within water

© 2013 Pearson Education, Inc. Molecular Attractions A dipole–induced dipole attraction is the attraction between a dipole and an induced dipole.

© 2013 Pearson Education, Inc. Molecular Attractions CHECK YOUR NEIGHBOR Is it possible for a fish to drown? A.no, because fish breathe water B.yes, when the water contains too little oxygen C.no, because water is 88.8% oxygen by mass D.yes, when the water is not moving Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. Molecular Attractions CHECK YOUR ANSWER Is it possible for a fish to drown? A.no, because fish breathe water B.yes, when the water contains too little oxygen C.no, because water is 88.8% oxygen by mass D.yes, when the water is not moving Explanation: Fish don't breathe water. Their gills extract the small amounts of dissolved oxygen, O 2, that can be found even in water that remains still.

© 2013 Pearson Education, Inc. Molecular Attractions CHECK YOUR NEIGHBOR A nonpolar material, such as oxygen, O 2, is soluble in a polar material, such as water, H 2 O, by way of A.ion–dipole attractions. B.dipole–dipole attractions. C.dipole–induced dipole attractions. D.all of the above Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. Molecular Attractions CHECK YOUR ANSWER A nonpolar material, such as oxygen, O 2, is soluble in a polar material, such as water, H 2 O, by way of A.ion–dipole attractions. B.dipole–dipole attractions. C.dipole–induced dipole attractions. D.all of the above Explanation: This is a relatively weak force of attraction, which explains why not much oxygen dissolves in the water. There is enough, however, to allow fish to live.

© 2013 Pearson Education, Inc. Molecular Attractions A fourth molecular attraction is the induced dipole–induced dipole, which occurs between nonpolar molecules.

© 2013 Pearson Education, Inc. Nonpolar atoms are attracted to each other by these "momentary" dipoles. Molecular Attractions

© 2013 Pearson Education, Inc. The larger the atom, the stronger the "momentary" dipole. Molecular Attractions

© 2013 Pearson Education, Inc. Molecular Attractions The tiny nonpolar fluorine atoms in Teflon provide very weak attractions, which is why Teflon provides a "nonstick" surface.

© 2013 Pearson Education, Inc. So, how do the gecko's sticky feet stay so clean? Molecular Attractions

© 2013 Pearson Education, Inc. Molecular Attractions CHECK YOUR NEIGHBOR Which type of molecular attraction takes the least amount of energy to break apart? A.ion–dipole attractions B.dipole–dipole attractions C.dipole–induced dipole attractions D.induced dipole–induced dipole attractions Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. Molecular Attractions CHECK YOUR ANSWER Which type of molecular attraction takes the least amount of energy to break apart? A.ion–dipole attractions B.dipole–dipole attractions C.dipole–induced dipole attractions D.induced dipole–induced dipole attractions Explanation: The induced dipole–induced dipole attraction is the weakest of the four, but only on a molecule-to-molecule basis. Remember, each hook on a strip of Velcro may be weak, but all the tiny hooks working together can provide significant holding power.

© 2013 Pearson Education, Inc. Most Materials Are Mixtures A pure substance is a material that consists of only one type of element or compound. A mixture is a collection of two or more pure substances. It can be separated by physical means.

© 2013 Pearson Education, Inc. Most Materials Are Mixtures

© 2013 Pearson Education, Inc. The Chemist's Classification of Matter

© 2013 Pearson Education, Inc. The Chemist's Classification of Matter Pure materials consist of a single element or compound. Impure materials consist of two or more elements or compounds. Mixtures may be heterogeneous or homogeneous.

© 2013 Pearson Education, Inc. The Chemist's Classification of Matter In heterogeneous mixtures, the different components can be seen as individual substances. In homogeneous mixtures, the composition is the same throughout.

© 2013 Pearson Education, Inc. The Chemist's Classification of Matter

© 2013 Pearson Education, Inc. The Chemist's Classification of Matter Homogeneous mixtures: –Solution: all components in the same phase –Suspension: different components in different phases

© 2013 Pearson Education, Inc. The Chemist's Classification of Matter CHECK YOUR NEIGHBOR Is the air in your house a homogeneous or a heterogeneous mixture? A.homogeneous, because it is mixed very well B.heterogeneous, because of the dust particles it contains C.homogeneous, because it is all at the same temperature D.heterogeneous, because it consists of different types of molecules Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. The Chemist's Classification of Matter CHECK YOUR ANSWER Is the air in your house a homogeneous or a heterogeneous mixture? A.homogeneous, because it is mixed very well B.heterogeneous, because of the dust particles it contains C.homogeneous, because it is all at the same temperature D.heterogeneous, because it consists of different types of molecules

© 2013 Pearson Education, Inc. Solutions A solution is a homogenous mixture consisting of ions or molecules. A solvent is the major component of a solution. A solute is the minor component of a solution. If a solution is saturated, then no more solute will dissolve in it.

© 2013 Pearson Education, Inc. Concentration Amount of solute Amount of solution Solutions Concentration is a measure of the amount of solute dissolved in solution. A solution with more solute than solution is called concentrated. A solution with more solution than solute is called dilute. =

© 2013 Pearson Education, Inc. The formula mass of a substance expressed in grams contains 1 mole. SubstanceFormula Mass Carbon, C12 Oxygen, O 2 32 Carbon dioxide, CO 2 44 Sucrose, C 12 H 22 O Solutions A mole is a super-large number, 6.02  10 23, used to measure numbers of atoms or molecules, also called Avogadro's number.

© 2013 Pearson Education, Inc. Sucrose, C 12 H 22 O 11 Solutions =342 g/mole

© 2013 Pearson Education, Inc. Solutions CHECK YOUR NEIGHBOR Water, H 2 O, has a formula mass of 18. How many moles of water are there in 18 grams of water? A.0.5 mole B.1 mole C.9 moles D.18 moles Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. Solutions CHECK YOUR ANSWER Water, H 2 O, has a formula mass of 18. How many moles of water are there in 18 grams of water? A.0.5 mole B.1 mole C.9 moles D.18 moles

© 2013 Pearson Education, Inc. Solutions CHECK YOUR NEIGHBOR How many grams of water, H 2 O, are there in 2 moles of water? A.1 gram B.9 grams C.18 grams D.36 grams Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. Solutions CHECK YOUR ANSWER How many grams of water, H 2 O, are there in 2 moles of water? A.1 gram B.9 grams C.18 grams D.36 grams

© 2013 Pearson Education, Inc. Molarity moles of Solute liter of Solution Solutions Molarity is a unit of concentration expressed in moles of solute per liter of solution. =

© 2013 Pearson Education, Inc. 1 ppm 1 part solute 1,000,000 parts solution 1 milligram solute 1 liter solution = Solutions ppm is a unit of concentration expressed in milligrams of solute in per liters of solution. =

© 2013 Pearson Education, Inc. Solubility Solubility is the ability of a solute to dissolve in a solvent. A solute that has appreciable solubility is said to be soluble.

© 2013 Pearson Education, Inc. Solubility A precipitate is solute that comes out of solution.

© 2013 Pearson Education, Inc. Solubility CHECK YOUR NEIGHBOR The amount of oxygen, O 2, dissolved in the waters of the Arctic Ocean is –––––––– the amount of oxygen dissolved in warm tropical waters. A.greater than B.about equal to C.less than D.It depends on other factors. Explain your answer to your neighbor.

© 2013 Pearson Education, Inc. Solubility CHECK YOUR ANSWER The amount of oxygen, O 2, dissolved in the waters of the Arctic Ocean is –––––––– the amount of oxygen dissolved in warm tropical waters. A.greater than B.about equal to C.less than D.It depends on other factors. Explanation: The solubility of oxygen in water decreases with increasing temperature. As a consequence, cold polar oceans tend to be more fertile than warmer tropical waters.

© 2013 Pearson Education, Inc. Chapter 12 Review CHECK YOUR NEIGHBOR By mass, water is 88.88% oxygen. So, why can't we breathe water? Hint: What is the elemental formula for the oxygen we breathe and the chemical formula for water? Explain your answer to your neighbor.