Chapter 6 Section 1 - 4

1. Chapter 6Section 1 - 4 Chemical Bonding

2. Chemical Bond… • A mutual __________ attraction between the _________ and __________________ of different atoms that binds the atoms together. • Most atoms are at a __________ energy state when bonded to other atoms rather than as independent particles

3. Types of chemical bonds: • Covalent • Covalent-network • Ionic • Metallic

4. Ionic bonding • Results from the ____________ attraction • between large numbers of _______ (+ ions) • and ___________ (- ions) Covalent bondingResults from the ____________ of electron pairs between 2 atoms

5. Ionic Bonding • _____________ differences in electronegativity values between atoms: • One atom attracts an e- so strongly that it actually PULLS IT AWAY from the other atom…electron is _______________ • Δ electronegativity > ________

6. Nonpolar Covalent Bond • Bonding electrons are shared ____________ by the bonded atoms, resulting in a balanced distribution of electrical charge • Δ electronegativity: ____________ (roughly)

7. Polar-covalent bond • Bonding electrons are shared ____________because one atom pulls, although not very strongly, more on the electron pair than the other atom • Δ electronegativity: ______________ • Still relatively small differences, so no atom really “wins” & e- is shared

8. Why would nature favor forming a covalent bond?

9. Attraction: nucleus of one atom to ______________ • Repulsion:both _____ repel…as do both _________ • As atoms approach, ____________ increases and potential E goes down • Beyond a certain point, ________________increases and E goes up ∴ bottom of valley on E curve is where there is a _______ between attraction & repulsion

10. MOLECULE: neutral group of atoms held together by _________________ bonds • MOLECULAR COMPOUND: a cmpd that is made of molecules • MOLECULAR FORMULA: shows the _____________ & ______________ of atoms making up a molecule i.e. H2O • DIATOMIC MOLECULE: molecule containing only ________ atoms i.e. H2

11. Characteristics of the Covalent Bond • Bond Length: average distance between 2 bonded atoms (min potential E) In the H2 molecule, the 1s orbitals overlap and result in a increased electron density between the nuclei.

13. Bond energy: • Energy required to ___________ a chemical bond and form neutral isolated atoms • Measured in __________________ • ________ value • Bond energy and bond length values will vary depending on what atoms an element is bonded to…ave values found on tables P.168)

14. Octet Rule • Chemical cmpds tend to form so that each atom, by gaining, losing or sharing electrons, has an ________________ of electrons in its highest (outermost) energy level • Example of exceptions: • H: only has 2 valence e-s required to reach stability • B: only has 6 valence e-s “ “ • Some elements have > 8 (occurs when atom bonds with highly electroneg elements & some “d” e-s are involved in bonding

15. Electron Dot Diagrams • Electron configuration notation in which only the valence electrons of an atom of a particular element are shown, indicated by dots placed around the element’s symbol • F:

17. “other” dot diagram format • Mg: [Ne]3s2 • “paired” electrons are shown as a pair

18. Lewis Structures • Formulas in which…. • atomic symbols are represent ___________________________________ • Dot-pairs or dashed between 2 atoms represent _____________________________ • Dots adjacent to only one atomic symbol represent _____________________________

19. Lewis structure Structural Formula: indicates the kind, number, arrangement,and bonds .. but NOT the unshared pairs of the atoms in a molecule

20. Lewis structure Single bond: covalent bond produced by the sharing on ONE pair of electrons between 2 atoms

21. Draw the Lewis structure for the following molecules: • IBr • CH3Br • F2O • SiCl4 • C2HCl (????)

22. Multiple Covalent Bonds • DOUBLE BOND • sharing of ___ pairs of electrons between 2 atoms • TRIPLE BOND • sharing of _____ pairs of electrons between 2 atoms • Bond Energies • triple double single • …..triple bonds are _________ and _______

23. Resonance Structures • bonding in molecules or ions that cannot be correctly represented by a single Lewis structure

24. Covalent-network Bonding Covalent bonding exists throughout a large network of atoms…will be discussed in chapter 12 i.e. carbon atoms in a diamond

25. Ionic Compound • composed of positive and negative ions that are combined so that the number of positive charges are equal to (cancel out) the number of negative charges • Na+1Cl-1 • Mg+2Cl2-1 (Mg+2Cl-1Cl-1) • Not called “molecules”…but called _____________________________

26. Formation of Ionic Cmpds • Atoms form ions when they ______________ e- in order to attain _________________________ • Ions reach a ____________ potential E through the electrical forces of attraction between oppositely charged particles when they combine in an orderly arrangement known as a _____________ • Forces of repulsion (like-charged ions, adjacent e- clouds) _____________ the forces of attraction (opp-charged ions, nuclei-electron of adj. ions)

27. Sodium chloride, NaCl • The chemical formula of an ionic cmpd is the simplest formula of the cmpd…it does NOT represent a discrete GROUP of separate atoms like a molecule does • Covalent bonding: simplest unit is a ________________ • Ionic bonding: simples unit is a _________________________

28. “Molecules” – discrete gps of atoms covalently bonded “Formula units” – simplest collection of atoms within an ionic cmpd i.e. NaCl..Na+1 doesn’t “belong” to any one neighbor

29. Lattice Energy • Term used to describe ___________ in ionic cmpds • Energy ____________________ when one of an ionic crystalline cmpd is formed from gaseous ions • _________ value indicates that E is ________ • The __________ the value, the more E released, the more stable the bonding will be (true also for bond E) • i.e. NaCl –787.5 kJ/mol

30. Which ionic cmpd has a higher melting point….MgO or CaO ?

31. IONIC strong force that holds _________________ stronger forces of attraction _____________ ions ∴_________ melting & boiling pts; don’t vaporize at room temp MOLECULAR strong covalent bond ____________________________________ _______ F of attraction ___________ molecules ∴melt at __________ temps & many vaporize at room temp Ionic vs. Covalent Properties

32. Other ionic properties… • ________________:tough for one layer to slide past another layer • ______________: if ionic layers DO shift, they “snap” when part of their crystal lattice is shifted

33. IONIC non-conductors in solid state because _________________ conductors in ______________ state conductors when _________________ MOLECULAR non-conductors in ________________ Ionic vs. Covalent Properties

34. Polyatomic Ions • A ______________ group of ____________ bonded atoms • Combine with ions of opposite charge to form __________________ cmpds

35. Draw the Lewis structure for the phosphate ion

36. Metallic Bond Model • Metals have _______________ electrons in their highest E level • Metals frequently have many _________________________________ • Vacant orbitals of adjacent atoms overlap which allows _________________________________

37. Metallic Bond Model (con’t) • “_________________ electrons” - e-s don’t stay in one locality like… • covalent bonding: stay in the ________________________________ • Ionic bonding: e-s are bound to ________________________________ • mobile electrons form a “________ of electrons”

38. Metallic Bonding • the chemical bonding that results from the attraction between ___________________________________ • ______________ sharing of many e-s where each atom contributes its valence e-s which are then free to move about the mostly vacant outer orbitals of all the metal atoms

39. Metallic Properties • __________electrical & thermal conductivity • due to high mobility and delocalization of e-s • _____________ (shine) • metals absorb E and become “excited” very easily because many of their orbitals are separated by extremely small ∆E…shine occurs when photons are emitted when excited e-s return to ground state

40. Metallic Prop. (con’t) • _______________________ (ability to be hammered/beaten into thin sheets) and ____________________ (ability to be drawn, pulled, or extruded to produce wire) because metallic bonding is the same in all directions and a shift in layers of atoms is inconsequential

41. Metallic Bond Strength • Expressed in the _________________value where the bonded atoms in the metallic solid state are converted into ___________________ metal atoms in the gaseous state (usually↑heat of vap, the ____ the bond strength) • Determined by • ___________________________________