Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Bond Energies Types of Chemical Bonds Chapter 8 Bond Energy • The strength of the interaction between atoms can be measured by the amount of energy it takes to break that bond. • Atoms form ions. • Ions are attracted to oppositely charged ions. • Cations and anions form ionic compounds Ionic Bonds Ionic Bonding • Metals and non metals form ionic bonds. • The degree of ionic bonding depends on the nature of the elements in the compound. • Ionic compounds are often called salts. Coulomb’s Law • The energy of an interaction between a pair of ions can be calculated. • k= 2.31 x 10-19 Jnm Why do ions form? • The ion pair in a compound has lower energy that the separated ions. • What is the energy of NaCl when the distance between the nuclei is 2.76 A or 0.276 nm? Answer: • E=(2.31 x 10-19 Jnm)[(+1)(-1)/(0.276 nm)2] • = -3.03 x 10-18 J • Coulomb’s Law may also be used to find the Energy of the repulsion between two like charged ions. Covalent Bonding • What about atoms with like charges? • When two H’s are brought together, they actually repulse. • Under what conditions will they bond? Covalent Bonds • When they are too close the repulsive force of the nuclei increases the energy. • When they are too far apart the energy is zero. • At the bond length, the energy is lowest and bonding occurs. Covalent bonding • When two or more elements share electrons. • When the electrons are shared equally, it is non polar covalent. Polar covalent bonding • When there is an unequal sharing of electron in a covalent bond. • Due to the relative electronegativity of the elements. Electronegativity Polar molecules • When there is an unequal sharing of electrons, partial charges form on the compound. • If that compound may align in an electric field, it is polar. Polar molecules Not in magnetic field & in magnetic field What makes a molecule polar? • Unequal sharing of electrons is due to differences in electronegativity. Relative polarities • Order the following bonds according to their polarity. • H-H; O-H; Cl-H; S-H & F-H • Answer: • H-H < S-H < Cl-H < O-H< F-H • 2.1-2.1; 2.5-2.1, 3.0-2.1, 3.5-2.1, 4.0-2.1 • 0 0.4 0.9 1.4 1.9 • Covalent Polar Covalent Bond