A simple pendulum consists of a small object of mass m (thebob) suspended by a cord of length (Fig. 7-32) of negligiblemass. A force F is applied in the horizontal direction(so F = Fi), moving the bob very slowly so the acceleration isessentially zero. (Note that the magnitude of F will need tovary with the angle 6 that the cord makes with the vertical atany moment.) (a) Determine the work done by this force, F, tomove the pendulumfrom 0 = 0 to6 = 60. (b) Determinethe work doneby the gravitationalforce on the bob,Fg = mg, and thework done by theforce Ft that thecord exerts on thebob.FIGURE 7-32 86.
Chapter 9 Chemical Bonding Models of Bonding Theories that can predict how and why different atoms will bond together are essential to chemistry because they can explain how the compound’s stability and shape o These theories have been helpful in the battle against HIV because they help in the creation of molecules that are able to bond to the protein that is essential to the development for HIV Different Types of Bonds Ionic- metal and nonmetal o Electron transfers from the metal to the nonmetal, the ions formed then attract each other and form a bond Covalent- nonmetal and nonmetal o Electrons are shared between the two nonmetals Metallic- metal and metal o Electrons become a pool around the metals Lewis model and Electron Dots In the Lewis Model chemical bonds are formed when electrons are transferred or shared in order to get a Noble Gas configuration Electron dots are the valence electrons around the elements symbol, when elements bond together the electron dots are shared or transferred to where both elements get eight electrons (octet rule) or a duet (two electrons) in the case of Hydrogen Ionic Lewis Structure and Lattice Energy In Lewis’ structure the main group of metals, the metal will transfer the electron to a nonmetal Most ionic formations are exothermic since there is lattice energy, energy released when a cation and anion bond together to form a solid. The smaller the radius of both ions the greater the charge therefore the lattice energy is exothermic. Covalent Structures, Polarity and Electronegativity Covalent structures the electrons are shared to obtain an octet formation Single shared electron pair has a single bond, while two to three paired electrons have a double or triple bonds respectively Electrons aren’t always equally shared o when two nonmetals bond that aren’t similar the most electronegative element has the greater electron density this results in a polar bond, one element has a partial positive charge while the other one has a partial negative charge Electronegativity- the ability of an atom to attract electrons in chemical bonding, increases as we move left to right across the periodic table but decreases as we move down. Elements with very opposite electronegativities will form ionic bonds those with similar electronegativities will form nonpolar covalent bonds intermediate electronegativities differences will form polar covalent bonds Pearson Mastering Chemistry