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Bonding Videos and Animations. Bonding. Intro to Ionic/Covalent Video. Bonding. What is the “goal” of atoms? What makes them happy? To achieve a filled valence shell. To do this, atoms must gain or lose electrons to form ions. Others share electrons.
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Bonding • Intro to Ionic/Covalent Video
Bonding • What is the “goal” of atoms? What makes them happy? • To achieve a filled valence shell. • To do this, atoms must gain or lose electrons to form ions. Others share electrons. • Ion- an atom that has gained or lost an electron, and therefore has a positive or negative charge based on the number of electrons it has lost.
The type of bond can usually be calculated by finding the difference in electronegativity of the two atoms that are going together.
Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. (How much an atom wants to gain an electron)
Electronegativity Difference • If the difference in electronegativities is between: • 1.7 to 4.0: Ionic • 0.3 to 1.7: Polar Covalent • 0.0 to 0.3: Non-Polar Covalent • Example: NaCl • Na = 0.8, Cl = 3.0 • Difference is 2.2, so • this is an ionic bond!
Ions • Cation- positively charged ion (loses e-) • Anion- negatively charge ion (gains e-)
Ionic Bonding • Ionic Bond- complete transferof 1 or more electrons from one atom to another (one loses, the other gains) forming oppositely charged ions that attract one another • Good Animation on Ionic Bonding
Covalent Bonding • Covalent Bond- some valence electrons are shared between atoms to achieve a “full” valence shell.
•• •• Cl H H Cl • • + • • •• •• Covalent Bond Formation A bond can result from an overlap of atomic orbitals on neighboring atoms. Overlap of H (1s) and Cl(3p) Note that each atom has a single, unpaired electron.
Review of Valence Electrons • Remember that valence electrons are the electrons in the OUTERMOST energy level… that’s why we did all those electron configurations!
So how can we write out a compound that is bonded? • 2 Methods: • Draw up the Lewis Dot Structures. • Swap Charges (works only for ionic) • How to Make Ionic Bonds
Lewis Dot Structure • Step 1, determine the # of valence electrons (either through group # for first 18 or through looking at electron configuration) • If you can lose them, then you get a + charge. Why? • If you need them, you get a (-) charge. Why? • Step 2, Then write the Atomic Symbol, surrounded by the electrons represented as dots.
Lewis Dot Structure Con’t • Step 3, place the dot structures next to each other (cationfirst if ionic bond). Then exchange dots.
Switch the Charges • Write each of the atoms with their charges. • Then swap the charges down to the front of the other atom to determine how many you need of each to balance out the charges. • Ex: Mg 2+ and Cl – make: MgCl2