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A QUICK BONDING REVIEW

A QUICK BONDING REVIEW. Why do atoms want to bond?. To achieve the octet rule OCTET RULE: atoms want to have 8 valence electrons in their outer most shell because it makes them stable. A bond is the link between two (or more) elements in a compound

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A QUICK BONDING REVIEW

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  1. A QUICK BONDING REVIEW

  2. Why do atoms want to bond? • To achieve the octet rule • OCTET RULE: atoms want to have 8 valence electrons in their outer most shell because it makes them stable

  3. A bond is the link between two (or more) elements in a compound Na---Cl it involves valence electrons A compound is what two (or more) elements linked together is called NaCl What is the difference between a bond and a compound?

  4. What are the different types of bonds and/or compounds? • IONIC • COVALENT • METALLIC

  5. IONIC BOND • bond between a metal and a nonmetal • involves transfer of electrons • one atom gains electrons (anion); the other atom loses electrons (cation) • attraction between oppositely charged ions holds ions together • strongest bond • the compound with an ionic bond is also called a FORMULA UNIT • example: the bond between sodium & chlorine in NaCl

  6. COVALENT BOND • bond between two nonmetals • there is “cooperation between valence electrons” or sharing of electrons • neither atom loses e- easily; both attract e- • by sharing e-, outer energy level is filled • attraction between nucleus and shared e- holds atoms together • strong bond, but weaker than ionic • the compound with a covalent bond is also called a MOLECULE • example: the bond between carbon & oxygen in CO2

  7. METALLIC BONDS • between 2 metals • positive nuclei of atoms surrounded by free-moving electrons • all electrons attracted by all the nuclei at the same time

  8. NAMING AND WRITING CHEMICAL FORMULAS

  9. Naming Ionic Compounds • Remember: between a metal & nonmetal fluorine  becomes fluoride sulfur  becomes sulfide oxygen  becomes oxide phosphorus  becomes phosphide nitrogen  becomes nitride iodine  becomes iodide

  10. Example: LiBr • Name metal: • Name nonmetal: • Add –IDE ending:

  11. CaCl2 Calcium chloride Notice that the subscripts do not matter in the name Rb2O Rubidium oxide More Examples

  12. Remember to use your Periodic Table! Writing Ionic Compounds • Remember ionic charges! (also called oxidation numbers) • Alkali metals (+1) • Alkaline Earth metals (+2) • Boron family (+3) • Nitrogen family (-3) • Oxygen family (-2) • Halogens (-1)

  13. Writing Ionic Compounds con’t

  14. Example: aluminum oxide • Determine each element’s charge: aluminum oxygen • Criss-cross the charges: (note: you may eliminate a subscript of 1)

  15. Lithium oxide Barium bromide = Li2O =BaBr2 More Examples

  16. What is a polyatomic ion? • It is an ion (or has a charge) and is composed of more than one element covalently bonded • Example: NO3–1 • This is the nitrate ion  the whole thing has a charge of –1 and it is composed of 1 nitrogen atom and 3 oxygen atoms See list on page 173).

  17. Naming Compounds… with polyatomic ions Remember that the subscripts do not matter in the name of IONIC compounds

  18. Example: Ca(NO3)2 • Name metal or positive polyatomic ion: • Name nonmetal or negative polyatomic ion: • Ca(NO3)2 

  19. NH4Br ammonium bromide Mg(OH)2 magnesium hydroxide More Examples

  20. Writing Compounds… with polyatomic ions • Use (parenthesis) if polyatomic ion has a subscript

  21. Example: barium perchlorate • Determine each charge: • Criss-cross:

  22. Potassium Cyanide K+1 CN-1 KCN Magnesium phosphate Mg+2 (PO4)-3 Mg3(PO4)2 More Examples

  23. Other thoughts… • Write the formula for beryllium sulfide • Beryllium: Be +2 Sulfide: S -2 you would think… Beryllium sulfide  Be2S2 But cancel subscripts to make….BeS

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