Bonding Lab Wrapping things up
Checking results: station 5 check below- your solutions may have been contaminated!
Station 7 Conclusion: Compounds w/ionic bonding contain metals & non-metals (ex: NaCl, Na=M, Cl=NM). Compounds w/metallic bonding contain only metals (ex: Zn=M). Compounds w/covalent or network covalent bonding are made of NMs (ex: Sugar=C6H12O6, C&H&O=NMs).
Bonds • Bonds = the attraction that holds atoms together • Two or more atoms may form bonds in order to make a compound • Example: the elements hydrogen (H) and oxygen (O) can form a bond to make the compound water (H2O) What am I doing here?
4 different types of bonds Network covalent ionic metallic Covalent (molecular)
Ionic “ion” = a charged particle • How these bonds form: • Metal atoms give up their valence electrons to the non-metals • Metals form positive ions (lose e-) • Non-metals form negative ions (gain e-) • Attraction due to opposite charges holds the atoms together
Properties of Ionic Compounds • Made of metal & non-metal atoms • Dissolve in water • Conduct electricity when dissolved • Do not conduct when solid • Brittle
Covalent (molecular) • How these bonds form: • Valence electrons are shared between groups of atoms • These groups of atoms are called “molecules”
Properties of Molecular Covalent Compounds • Made of nonmetals • Some dissolve in water, some don’t • Do not conduct electricity • Are liquids or gases or soft solids
Network covalent • How these bonds form: • Valence electrons connect atoms together in all directions- a giant network of connected atoms
Properties of Covalent Network Compounds • Made of nonmetal atoms • Do not dissolve in water • Do not conduct electricity • Very hard solids
Metallic • How these bonds form: • Electrons move freely, not associated with any particular atom • “Sea of electrons”
Properties of Metallic Compounds • Made of metal atoms • Do not dissolve in water • Conduct electricity • Are bendable solids
Ionic Bonds • Hold two ions together • Anion = negative ion • Cation = positive ion • Opposite charges attract Na + Cl- cation anion
Why do ionic solutions conduct? • Crystal lattice dissolves in water to form individual ions • Movement of ions allows current to flow
Why does tap water conduct electricity and not pure, de-ionized water? • Your tap water may have… • Chlorine • Dissolved minerals such as calcium and magnesium • Sodium • Fluoride H2O Na+ F- H2O Mg2+ Cl - Tap Water Pure Water
Bonding Animations http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/bom1s2_11.swf http://ithacasciencezone.com/chemzone/lessons/03bonding/mleebonding/default.htm
1. Which model would you predict for the following substances? Explain your reasoning. Molecular Covalent, it is made of non-metals & dissolves in water. Ionic, it is made of a metal & a non-metal. Ionic, it is made of a metal & a non-metal. Metallic, it is made of only metal atoms. Molecular Covalent, it is made of non-metals & is a gas.
2. In the ionic solid, Model 1, the non-metal atoms have a negative charge & the metal atoms have a positive charge. What do you think causes these charges? Gaining & losing electrons! Gaining electrons = negative charge Losing electrons = positive charge
3. In the metallic solid, Model 3, the “sea” of electrons has a negative charge. What charge would the spherical atoms have? Explain. Positive charge because they are attracting the “sea” of electrons.
4. In covalent substances electrons are shared between atoms. What differences do you see in Models 2 & 4? In Model 2, electrons are being shared between 4 atoms. In Model 4, electrons are only being shared between 2 atoms.
Use the models to explain the following evidence: • Molecular covalent substances are often gases • Ionic substances are brittle The atoms are not as connected so they can “fly away” as a gas. Because they don’t share electrons, they are not as connected & can break easily.
HMK Questions 1-4 on page 6
1. Compare & contrast each of the following pairs of bonding types with respect to i) the role of electrons in bonding and ii) physical properties of the bonded materials such as hardness: • Ionic bonding & covalent bonding In ionic bonding, electrons are transferred from a metal to a non-metal. In covalent bonding, electrons are shared between 2 non-metals. Substances with ionic bonding are solids and substances with covalent bonding are liquids or gases.
1. Compare & contrast each of the following pairs of bonding types with respect to i) the role of electrons in bonding and ii) physical properties of the bonded materials such as hardness: • Network covalent bonding & metallic bonding In network covalent bonding, electrons are shared between non-metals all around. In metallic bonding, atoms are surrounded by a sea of electrons. Substances with both of these types of bonding are hard solids. Only metals conduct electricity though.
2. You observed NO2(g) when you dissolved Cu(s) in nitric acid in the copper cycle lab. How would you classify the bonding in NO2 (g)? Explain. Molecular covalent because both N & O are non-metals & it’s a gas.
3. Think about the physical properties of the following substances, and decide which type of bonding you would probably find in each substance. Explain your reasoning. • a) hair gel • b) silver bracelet • c) motor oil • d) sodium bicarbonate Covalent—it’s a liquid. Metallic—it’s made of only metals. Covalent—it’s a liquid. Ionic—it’s a solid (& has metals & non-metals).
4. Look at the chemical makeup of the following substances & decide which type of bonding you would probably find in each substance. • a) Zn (s) zinc • b) C3H8 (l) propane • c) CaCO3 (s) calcium carbonate Metallic Covalent Ionic