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Chapter 19 Chemical Bonds

Chapter 19 Chemical Bonds. How does the nucleus of an atom stay together???. Forces act on it 1. electromagnetic force – opposites attract and like charges repel Helps explain electrons are attracted to the atom’s center. So why do protons stick together?.

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Chapter 19 Chemical Bonds

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  1. Chapter 19 Chemical Bonds

  2. How does the nucleus of an atom stay together??? • Forces act on it • 1. electromagnetic force – opposites attract and like charges repel • Helps explain electrons are attracted to the atom’s center

  3. So why do protons stick together? • A special force acts between protons and neutrons called the strong force • It is stronger than the electromagnetic force acting on an atom

  4. Chemical Formula- tells which elements are in a compound and their ratios Example NaCl H2O Chemical Symbol- short hand way of writing an element’s name Example C O Na Chemical Formula VS Chemical Symbol

  5. Chemical Formula • Try These: list the element and number of atoms • Hydrochloric Acid: HCl • Methanol: CH4O • Ethanol: C2H6O • Nitroglycerin: C3H5N3O9

  6. Activity • Your teacher will assign to you an element. • For that element complete the following on a sheet of white paper • Name and symbol • Draw an electron configuration • Draw an electron dot diagram • List the group number and period number

  7. Next • On the board place your element in the appropriate space on the PTOE

  8. Why do atoms form Compounds? • To become stable • In order to be stable an atom needs 8 outer electrons aka valence electrons • In order to become stable atoms form bonds to become a compound • Noble Gases/ group 18 are stable because they have a full outer orbital (8 outer electrons)

  9. Ionic Gains or loses electrons Covalent Shares electrons Types of bonds

  10. Let’s talk more about ionic bonds.. • What you already know… gains or loses electrons • But you don’t know… elements that are far away from each other on the PTOE will form ionic bonds • Metals form ionic bonds with nonmetals • Metals lend electrons and nonmetals gain them

  11. Ionic Bond Examples Potassium and Iodine Magnesium and Sulfur

  12. An atom that loses or gains electrons = ION • When an atom loses one or more electrons it is losing negative charges so it becomes a positive ion • When an atom gains one or more electrons it is gaining negative charges so it becomes a negative ion

  13. Let’s talk more about covalent bonds.. • What you already know… share electrons • But you don’t know… elements with larger number of electrons (4) need a lot of energy to lose them so the electrons are shared instead • The compound formed by sharing electrons is called a molecule • Elements close to each other on the PTOE will form covalent bonds (usually nonmetals)

  14. Covalent Bonding • Covalent Bonding- Electrons are shared • Nonpolar bonds- Electrons are shared equally • Polar Bonds- Electrons are not shared equally

  15. Covalent Bond Examples • Hydrogen and Oxygen • Hydrogen and Chlorine • Hydrogen and Fluorine

  16. Carbon and oxygen Sodium and oxygen P and oxygen Mg and oxygen Al and oxygen Cl and oxygen Sulfur and oxygen Ionic Covalent Why? Which type of bond will these elements form?

  17. Oxidation number • Positive or negative number that indicates how many electrons an atom has gained, lost or shared to become stable • The oxidation number is the same as the charge on an ionic compound • Used to write formulas • Example • Na ion has a charge of 1+ so its oxidation number is 1 +

  18. PToE and Oxidation Numbers • Open books to page 588 and take out your PToE from your binders • Oxidation Numbers Practice on board/in student notes

  19. Writing Formulas • Remember: • Compound are neutral • Sometimes you need to simplify Use Worksheet titled: Crisscross method for instructions for formula writing

  20. Binary IonicCompounds= composed of 2 elements Polyatomic ions = positive or negative group of covalently bonded atoms that bond to another element Has more than 2 elements

  21. Naming Binary Ionic Compounds • First write name of positive ion • Next the root of the negative ion and add –ide to the end of it • Examples: oxygen = oxide nitrogen = nitride

  22. Naming Polyatomic Compounds • Same as binary but the negative ion ends in -ate

  23. Naming Binary Covalent Compounds • Formed between nonmetals • Uses prefixes to identify how many atoms of each element there are • Look at page 593 and learn these prefixes • Examples: • N2O dinitrogen oxide

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