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Warm-up

Warm-up. Determine the number of valence electrons and the charge of an atom of these elements: Example: Chlorine: 7 valence electrons and -1 charge Beryllium Be: 2 valence and Be +2 Sulfur S: 6 valence and S -2 Fluorine F: 7 valence and F -1 Oxygen O: 6 valence and O -2. Chemistry.

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Warm-up

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  1. Warm-up • Determine the number of valence electrons and the charge of an atom of these elements: • Example: Chlorine: 7 valence electrons and -1 charge Beryllium Be: 2 valence and Be+2 Sulfur S: 6 valence and S-2 Fluorine F: 7 valence and F-1 Oxygen O: 6 valence and O-2

  2. Chemistry Unit Four, Day One Kimrey 26 September 2012

  3. Chemical Bonding Its what happens when elements fall in love!

  4. 3 Types of Bonds • Covalent bonding • Ionic bonding • Metallic Bonding

  5. Covalent Bonding-The perfect relationship • Bond is formed by the sharing of electrons between two nonmetals. • Two types of covalent bond polar and nonpolar. • Polar covalent bond- unequal sharing of electrons. • Nonpolar covalent bond- equal sharing of electrons.

  6. Ionic bonding-The stage five clinger • One element steals all the electrons from another. -or more technically • A transfer of valence electrons between a cation (+) and an anion (-). • Typically between a metal and nonmetal or a metal and polyatomic ion. ex. NaCl, LiF, CaF2 • Polyatomic ion- a group of bonded atoms that have a charge. ex. OH-, SO42-, etc.

  7. Metallic Bonding-when two people merge into one. • Between two metals and forms a sea of electrons. • Attraction between the positive nucleus and surrounding electrons. • Forms a sea of electrons. • This is why metals are malleable and ductile. • Electrons don’t belong to either element – instead just float around the nuclei

  8. CATION ANION Answer these questions: An atom that gains one or more electrons will have a ____________________ charge. An atom that loses one or more electrons will have a ____________________ charge. An atom that gains or loses one or more electrons is called an ____________. A positive ion is called a ______________ and a negative ion is called an _______________. NEGATIVE POSITIVE ION

  9. What is an ionic bond? Atoms will transfer one or more ________________ to another to form the bond. Each atom is left with a ________________ outer shell. An ionic bond forms between a ___________ ion with a positive charge and a ________________ ion with a negative charge. Example B1: Sodium + Chlorine Example B2: Magnesium + Iodine ELECTRONS COMPLETE METAL NONMETAL

  10. What is a covalent bond? Atoms ___________ one or more electrons with each other to form the bond. Each atom is left with a ________________ outer shell. A covalent bond forms between two _________________. Example C1: Hydrogen + Hydrogen Example C2: 2 Hydrogen + Oxygen SHARE COMPLETE NONMETAL

  11. Electronegativity • The ability of an atom in a compound to attract valence electrons to itself. • Scale of 0-4 • Differences in electronegativity is used to determine the type of bond. 0-0.4 = Nonpolar covalent 0.4-1.7 = Polar Covalent 1.7-4.0 = Ionic • Example: Sodium bonded to bromine

  12. Practice • Identify the following bonds as polar or non-polar covalent: • Hbonded to O • H bonded to C • C bonded to F • C bonded to N

  13. Formulas for Ionic Compounds • Ionic compounds will bond in a ratio that cancels their ion charge • ALL compounds no matter what are neutral

  14. Steps for Writing Formulas • Find the charges of the elements. • Find the simplest ratio needed to cancel out the charges. • Write the ratio numbers as subscripts (ones do not get written!) • Write the positive ion first followed by the negative ion. Make sure not to write the charges of the ions in the formula.

  15. Examples • Sodium and Chlorine NaCl • Potassium and Iodine KI • Calcium and Bromine CaBr2 • Barium and Oxygen BaO

  16. Those pesky polyatomics. • Polyatomic is a group of bonded atoms that still has a charge. • Same steps as binary compoundsplus… 5. If a subscript is added to a polyatomic ion place the entire polyatomic in (). REMEMBER! Never ever change the subscripts in a poly-atomic ion.

  17. Examples • Sodium and Hydroxide (OH-1) NaOH • Lithium and sulfate (SO4-2) Li2SO4 • Calcium and phosphate (PO4-3) Ca3(PO4)2 • Ammonium and fluorine (NH4+1) NH4F

  18. What does all this mean? • The chemical formula tells you the number of each element in that compound.

  19. 1. Complete the chart using your knowledge of atoms. Vocab Review 1 – What do we call the electrons in the outermost energy level? 2 – What term refers to an atom that has lost or gained electrons? 3 – What is a cation? 4 – What is an anion? Valence Electrons Ions A positively charged ion A negatively charged ion

  20. 2. Ionic Bonds - Draw the Lewis structures for each atom, draw arrows to show the transfer of electrons, write the charge for each ion, and then write the chemical formula. (A) Potassium + Iodine (B) Magnesium + Oxygen (C) Lithium + Nitrogen

  21. 3. Covalent Bonds – Draw the Lewis structures for each atom, draw circles to show the electrons that are shared, and then write the bond structure and chemical formula. (A) Fluorine + Fluorine (B) 3 Hydrogen + 1 Phosphorus (C) 2 Hydrogen + 1 Sulfur

  22. Potassium + Iodine Sodium + Oxygen Calcium + Chlorine Aluminum + Chlorine

  23. Chlorine + Chlorine Oxygen + Oxygen Carbon + 2 Oxygen Carbon + 4 Hydrogen

  24. What about other metals? • Other metals charges will always be given in roman numerals. e.g. I,II, IV • These charges are always positive. • What is the charge of Iron (II)? 2+

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