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Chapter 7

Sodium chloride. Nitrogen dioxide. Chapter 7. Carbon monoxide. Hydrochloric acid. Calcium fluoride. Ionic and Metallic Bonding. Magnesium sulphate. Hydrogen peroxide. MOLECULAR VS. IONIC COMPOUNDS. MOLECULAR COMPOUNDS: 1. Low melting & boiling points

karen-nichols
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Chapter 7

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  1. Sodium chloride Nitrogen dioxide Chapter 7 Carbon monoxide Hydrochloric acid Calcium fluoride Ionic and Metallic Bonding Magnesium sulphate Hydrogen peroxide

  2. MOLECULAR VS. IONIC COMPOUNDS MOLECULAR COMPOUNDS: 1. Low melting & boiling points 2. Solids, Liquids, and Gases at room temp. 3. Sharing of valence electrons 4. Two or more Nonmetallic elements 5. Contain covalent bonds EX: H2O CO2

  3. MOLECULAR VS. IONIC COMPOUNDS IONIC COMPOUNDS: 1. High melting & boiling points 2. Composed of ions (cation and anion) 3. Electrically neutral 4. Crystalline solids at room temperature -coordination #, 3D patterns 5. Composed of a Metal and Nonmetal 6. Contains Electrostatic Bonds EX: NaCl MgCl2

  4.                                             Ionic Bonds: One big greedy thief dog! Ionic bonding can be best imagined as one big greedy dog steeling the other dog's bone.  If the bone represents the electron that is up for grabs, then when the big dog gains an electron he becomes negatively charged and the little dog who lost the electron becomes positively charged.  The two ions (that's where the name ionic comes from) are attracted very strongly to each other as a result of the opposite charges.

  5. CHEMICAL FORMULA: Shows the kinds and number of atoms in the smallest representative unit of the substance.

  6. IONIC FORMULA: 1. Ionic compounds exist as formula units. 2. Shows the lowest whole-number ratio of ions present in an ionic compound (formula unit). EX: NaCl (sodium chloride) Na+1 Cl-1 1:1 ratio MgCl2 (magnesium chloride) Mg+2 Cl-1 1:2 ratio

  7. Ionic Compounds

  8. How to Write an Ionic Formula: 1. Write down symbols 2. Determine Ionic Charges 3. Charges must cancel each other out (equal zero) • if not, use criss-cross method to form subscripts to cancel out charges

  9. Potassium Bromide K+1 Br-1 charges cancel KBr Magnesium Oxide Mg+2 O-2 charges cancel MgO EXAMPLES: Aluminum Nitride Al+3 N-3 charges cancel AlN Magnesium Chloride Mg+2 Cl-1 charges don’t cancel, criss-cross MgCl2 Sodium Sulfide Na+1 S-2 charges don’t cancel, criss-cross Na2S Aluminum Oxide Al+3 O-2 charges don’t cancel, criss-cross Al2O3

  10. Naming an Ionic Formula: 1. Write the name for the metal and nonmetal 2. Check to see if the metal has more than one charge (Cu, Fe, transition metals) 3. If metal has more than one charge, you must do a “reverse” criss-cross to determine formula • A Roman Numeral goes between the two names 4. Change the nonmetal ending to IDE

  11. KBr potassium bromide Na2O sodium oxide EXAMPLES: MgS magnesium sulfide Cu Br2 copper II bromide As2 O5 arsenic V oxide Fe2 O3 iron III oxide

  12. Metallic Bonds

  13. Consist of the attraction of the free-floating valence electrons for the positively charged metal ions. Lets Remember: • Good conductors of electricity & heat • Ductile & malleable • Metals have 1,2, or 3 valence electrons • Low ionization energies : (easy to remove valence electrons)

  14. Cation Sea of valence electrons Therefore: 1. Valence electrons don’t belong to any individual atom. 2. Valence electrons exist as a sea around closely packed metal cations.

  15. Cation Sea of valence electrons 3. Metal cations are insulated from one another by a sea of drifting valence electrons (ballbearings in oil) 4. Metals are simplest crystalline solids 5. Orderly compact pattern

  16. Metallic Bonds:  Mellow dogs with plenty of bones to go around These bonds are best imagined as a room full of puppies who have plenty of bones to go around and are not possessive of any one particular bone.  This allows the electrons to move through the substance with little restriction.  The model is often described as the "kernels of atoms in a sea of electrons."

  17. Laws of Proportions I. Law of Definite Proportions: A chemical compound always contains the same elements in exactly the same proportions by mass. Any two samples of a given compound are made of the same elements in exactly the same proportions by mass.

  18. Law of Definite Proportions: EX: H2O 2g 16g 1:8 mass ratio always for any compound of water CO and CO2

  19. Laws of Proportions II. Law of Multiple Proportions: (comparing 2 different cmpds) When two elements combine to form two or more compounds, the mass of one element that combines with a given mass of the other is in the ration of small whole numbers.

  20. Law of Multiple Proportions: EX: Carbon reacts with oxygen to form 2 cmpds. Cmpd. A contains 2.41 g of C for each 3.22 g of O. Cmpd. B contains 6.71 g of C for each 17.9 g of O. What is the lowest whole number ratio of C that combines with a given mass of oxygen?

  21. Law of Multiple Proportions: EX: Two compounds that contain H and O are hydrogen peroxide and water. 1. Demonstrate the Law of Definite Proportions for these two compounds. 2. Find the mass ratio of oxygen in these 2 cmpds.

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