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Basics of Chemical Bonding

Basics of Chemical Bonding. and the Energetics of Chemical Bonding. A few main ideas about bonding and energy…. A chemical bond is a ________ 1 _________ that holds two atoms together. Chemical bonds involve the ____ 2 ____ or ____ 3 _____ of one or more electrons between two atoms.

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Basics of Chemical Bonding

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  1. Basics of Chemical Bonding and the Energetics of Chemical Bonding

  2. A few main ideas about bonding and energy…. • A chemical bond is a ________1_________ that holds two atoms together. • Chemical bonds involve the ____2____ or ____3_____ of one or more electrons between two atoms. • There are 3 main types of chemical bonds:_____4____, _____5____, and ____6____. • Nature prefers __7__ energy. Low ____8_____ energy equals high ___9______. Chemical bonding allows each atom involved to reach a lower potential energy state and achieve greater stability.

  3. A physical analogy to better understand the energetics of chemical bonding… Ball at top of hill – high potential energy, low stability i.e. unstable Ball at base of hill – lower potential energy, higher stability i.e. more stable Increasing Potential Energy

  4. The main point here is that ….. • Through the process of chemical bonding (which allows atoms to achieve stable octets/duets in the ____10____ shell), atoms get to a lowerchemical potential energy state. Chemical potential energy is stored within the matter by virtue of the ______11_____ of its particles and via the chemical bonds between particles. • Thus, chemical bonding of atoms to form compounds is always an ______12______ process! It releases energy from the ___13____ to the _____14______.

  5. Video Clip – The formation of NaCl • NaCl sodium chloride is an ionic compound formed via the chemical reaction: 2Na(s) + Cl2(g)  2NaCl “Two moles of sodium atoms react with one mole of chlorine gas molecules to form 2 moles of sodium chloride formula units”

  6. The Basics of an Ionic Bond • An ionic bond is an attraction between oppositely charged ___15___. • In an ionic bond, a ____16____ atom gives away one or more electrons from its valence shell to form a ____17____. A _____18_____ atom steals these same electrons to complete its valence shell and form an ____19____. The oppositely charged ions that form then ____20____ together to form the ionic compound..

  7. Flowchart of the Ionic Bond Formation Process

  8. Diagramming Ionic Bond Formation with Electron Dot Diagrams

  9. Basics of the Ionic Bond - Continued • The essence of the ionic bond is the ______21______ (postive-negative) attraction between the newly formed cations and anions after electron ____22____ has occurred. • The resulting pure substance, made of metallic and nonmetallic atoms bonded together, is called an ________23_________. • The number of ____24____ charges balances the number of ____25____ charges so that the ionic compound is ____26____ or charge- ____27_____. It is neither positive or negative as a whole, though it is made of __28__ inside!

  10. Ionic Compounds – Crystal Lattice Structure NaCl (sodium chloride) MgBr2 (magnesium bromide)

  11. Ionic Compounds - Structure • When cations and anions join together, they never form ____29_____. Instead, they join up as a continuous, 3-d, geometric structure known as a ______30________. • In the crystal lattice, each ___31___ is surrounded only by neighboring ___32___ and vice versa. This is necessary in order to prevent + + or - - repulsions that would break the lattice apart.

  12. Ionic Compounds – Structure and Representative Particles • The representative particle of an ionic compound is a _______33_______. • It tells us what the lowest, whole-number ___34___ of cations to anions is in the crystal structure. • The simplest repeating, piece of any crystal lattice is a _____35_____. It is also represented by a formula unit.

  13. Lattice Energies of Ionic Compounds • Lattice energy is the amount of energy _____36______ when one __37__ of an ionic compound forms a crystal lattice structure during a chemical reaction between the constituent metallic and nonmetallic atoms. (Units of kJ/mol) • Since energy is released from the chemical system to the surroundings (i.e. exothermic), the sign for lattice energy is always ____38____!

  14. Lattice Energies of Ionic Compounds (continued) • In order to break apart a crystal lattice back into the constituent atoms, we would need to put that energy back into the chemical system. • Thus, breaking bonds is _____39_____! (It always takes energy to break things!) • The energy to break bonds is called ______40_______. • For ionic compounds, the bond energy per mole of the compound is equal to the lattice energy but _____41_____ in sign.

  15. Illustrating Lattice Energy vs. Bond Energy

  16. What can we infer from lattice energies of ionic compounds?

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