{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Aligns in an electric field aligns polar molecules

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ic charge and the H Example HF atom a slightly charge of equal magnitude. Aligns in an electric field. Aligns Polar molecules posses a Polar 12/04/09 Zumdahl Chapter 13 , μ. 9 Electronegativity (EN) vs. Electron Affinity (EA) • Electron affinity is a measure of the energy required to detach an electron from an atom or molecule: detach A− → A + e− , ∆ E ≡ EA EA (a large EA means a strong attraction of electrons) means • Electronegativity is a measure of the ability of an atom in a molecule to attract shared electrons to itself. in shared 12/04/09 Zumdahl Chapter 13 10 The Person Behind the Science Linus Pauling (1901-1994 ) Moments in a Life 1954 Nobel Prize in chemistry 1954 – Chemical Bonding, molecular biology • 1962 Nobel Peace Prize 1962 – Health (Vitamin C advocate) and Health Nuclear testing (banning atmospheric tests ) tests Electronegativity Scale: concept of partially ionic bonds. – fluorine with x = 4 is the most electronegative element, francium with x = fluorine 0.7 the least. Percent Ionic Character – x values can also be used to estimate the dipole moment and ionic character of bonds. character Pauling: Electronegativity is the power of an atom in a molecule to attract in electrons to itself. – x differs from the electron affinity of the free atom although the two run of roughly parallel. roughly 12/04/09 Zumdahl Chapter 13 11 • • • • The Pauling Electronegativity Values The as Updated by A.L. Allred in 1961 as Note: Note: 12/04/09 Zumdahl Chapter 13 12 Expected H−X bond energy = 1/2 [(H−H bond energy) (X−X bond energy)]1/2 [( (Geometric Mean of H−H and X−X Bond Energies) (Geometric Bond energy = expected bond energy if Bond expected Δ = EN(H) −EN(X) = 0. The larger Δ is, the stronger the H−X bond is. Ionic vs. Covalent Bonding 12/04/09 Zumdahl Chapter 13 13 Dipole moment: μ = Q r 1 debye(D)= 3.34*10^-30Cm Ionic Character = 100% if μ = Q r where where r = bond length (μ & r det’d experimentally) det’d bond Q = electron charge electron 12/04/09 Zumdahl Chapter 13 14 Non-Polar Covalent Non-Polar Bonding Bonding 12/04/09 Zumdahl Chapter 13 15 Ca: [Ar]4s2 Ca: [Ar]4s O: O: 12/04/09 Lose 2 electrons Ca2+: [Ar] or [Ne] [He] [He] 2s22p4Gain 2 electrons O2−: [He] 2s22p6 [He] Zumdahl Chapter 13 16 Sizes of ions related to positions of elements in the periodic table. Atomic Radii In In picometers picometers Cations: smaller Cations: than parent atom than Anions: larger than parent atom than Isoelectronic series: series: O2FNa+ Mg2+ 12/04/09 Zumdahl Chapter 13 Al3+ 17 Formation of Binary Ionic Compounds Step 1: Vap. Of Li Step 2: Ion. Of Li Step 3: Dissoc. Of F2 Step 4: Electron Affinity for F Step 5: Lattice energy of LiF(s) Lattice Energy (5) can be calculated using a modified version of Coulomb’s Law (see text, p. 229) (see Li(s) + ½ F2(g) LiF(s) Li(s) 12/04/09 Zumdahl Chapter 13 18 Partial Ionic Character of Covalent Bonds Percent Ionic Character Covalent e.g., H2, Cl2 N2 Polar Covalent e.g., HF, H2O The relationship betwe...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online