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Covalent Bonding

Covalent Bonding. I CAN write a formula for and name a covalent (molecular) compound. Covalent Bonds. Recently we worked with IONIC COMPOUNDS which form when positive CATIONS combine with negative ANIONS . Not ALL compounds involve ions.

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Covalent Bonding

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  1. Covalent Bonding LecturePLUS Timberlake

  2. I CAN write a formula for and name a covalent (molecular) compound. LecturePLUS Timberlake

  3. Covalent Bonds • Recently we worked with IONIC COMPOUNDS which form when positive CATIONS combine with negative ANIONS. • Not ALL compounds involve ions. • In COVALENT BONDING, valence electrons are shared between two atoms. • Electrons are NOT transferred from one atom to another, so they do not develop “+” or “-” charges as do ions. • Generally form between TWO NONMETAL ELEMENTS from GROUPS 14, 15, 16, and 17 but can involve elements FROM OTHER GROUPS. • Covalent compounds are also called MOLECULAR COMPOUNDS. LecturePLUS Timberlake

  4. EXAMPLE Two Hydrogen atoms move close together to SHARE valence electrons. H+H H H LecturePLUS Timberlake

  5. The SAME TWO ATOMS can share DIFFERENT NUMBERS of electrons. • There is more than one possible formula combination for the same group of atoms. For example, NITROGEN and OXYGEN can form several different compounds: NO NO2 NO3 N2O N2O2 N2O3 N2O4 N2O5 If we named this NITROGEN OXIDE, which one would we be talking about? LecturePLUS Timberlake

  6. Naming Covalent (Molecular) Compounds In order to name a COVALENT compound, we follow the same basic rules as for BINARY IONIC compounds….with one added step. Since the same group of atoms can bond in different proportions, we must indicate HOW MANY OF EACH ATOM there is in the compound. LecturePLUS Timberlake

  7. Naming Covalent Compound • 1. Name the first element by its name, adding a NUMBER PREFIX ONLY IF THERE IS MORE THAN ONE ATOM. • 2. Name the second element by its name, but: • A. Change the ending to IDE. • B. Add a NUMBER PREFIX to tell how many, even if there is only one! LecturePLUS Timberlake

  8. Number Prefixes for Covalent Compounds 1 – Mono 2 – Di 3 – Tri 4 – Tetra 5 – Penta 6 – Hexa 7 – Hepta 8 – Octa 9 – Nona 10 –Deca LecturePLUS Timberlake

  9. When adding prefixes, the “A” or “O” of the prefix may need to be DROPPED if the element starts with a VOWEL, such as: • Hexa added to OXIDE becomes: • Hexoxide NOT Hexaoxide LecturePLUS Timberlake

  10. Practice Problems Example Write the formula for: TrinitrogenPentachloride Tri = 3Penta = 5 nitrogen chloride = chlorine So this compound needs 3 NITROGEN and 5 CHLORINE The 3 and 5 are the SUBSCRIPTS in the formula. N3Cl5 LecturePLUS Timberlake

  11. WRITE the formula for these Covalent Compounds: (To make it easier, prefixes are colored in these practice problems) Click HERE for a PERIODIC TABLE. 1.carbonmonoxide 2.carbondioxide 3.phosphorustrichloride 4.carbontetrachloride 5.dinitrogenmonoxide LecturePLUS Timberlake

  12. 1. CO carbon monoxide 2. CO2 carbon dioxide 3. PCl3phosphorus trichloride 4. CCl4 carbon tetrachloride 5. N2O dinitrogen monoxide LecturePLUS Timberlake

  13. MORE PRACTICE PROBLEMSWrite the correct formula for the following Covalent compounds. 1. triphosphorusmonoxide 2. phosphoruspentoxide 3. diphosphoruspentoxide 4. dichlorineheptoxide 5. dichlorinetribromide 6. silicontetroxide 7. carbontribromide 8. antimonydisulfide LecturePLUS Timberlake

  14. Diatomic Elements • Some elements, when not bonded to other elements, bond to another atom of their own kind. These are known as DIATOMIC ELEMENTS. • There are 8 naturally existing diatomic elements: • ALL of family 17 (Halogen Family). • Oxygen, Nitrogen and Hydrogen • These elements should be written as: • F2, Cl2, Br2, I2, At2, O2, H2, N2 when they are NOT part of a compound.

  15. Pure vs Polar Covalent • When two atoms share an electron, the ELECTRONEGATIVITY value of each atom determines how closely the electron is pulled toward one atom or the other. • Recall Electronegativity [Eneg] is the measure of the attraction one atom has for another’s valence electrons. • SEE CHART NEXT SLIDE FOR Eneg Values. LecturePLUS Timberlake

  16. Electronegativity Values LecturePLUS Timberlake

  17. Determining Bond Type • To determine the type bond between any two atoms, find the difference between their Eneg values: 0 to 0.5 - PURE Covalent – the e- is shared at an equal distance between both atoms. 0.51 to 1.99 – POLAR Covalent – the e- is shared closer to one atom than the other…this gives the atom the e- is closest to a slightly NEGATIVE charge [delta -] and the one the e- is father away from a slightly POSITIVE charge [delta +]. 2.0 or greater – the e- is completely transferred from one atom to the other and forms an IONIC BOND. LecturePLUS Timberlake

  18. Practice Problems • Use Eneg values to predict the type of bond that would form between each pair of atoms: • 1. Ca and Br ____________ 2. H and O ______________ 3. Pb and S ______________ 4. Au and S_______________ 5. Sn and I ______________ 6. C and H _______________ • 7. B and H _______________ 8. Fr and F _______________9. N and Al _______________ LecturePLUS Timberlake

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