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Explore the concept of chemical bonding and how atoms are attracted to each other to form molecules. Learn about ionic and covalent bonds, and understand the importance of electrons in determining the bonding patterns.
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Bell Ringer • How do you think H and O in water are bonded together? • Draw a picture to help your explanation.
Chemical Bond 8
Bonding Introduction to Chemical Bonding
Bonding: the way atoms are attracted to each other to form molecules, determines nearly all of the chemical properties we see. And, as we shall see, the number “8” is very important to chemical bonding. I want you to meet a friend of mine?
What are Molecules? Molecules are a combination of atoms bonded together. Bonding determines the chemical properties of the molecule (compound).
Intro to Bonding • There are several types of chemical bonds. • Covalent bonds polar and non polar • Ionic bonds • Hydrogen bonds • Metallic bonds
Chemical Bonds • atoms rarely exist alone • when atoms are bonded together, they have less potential energy and are more stable • What is potential energy? • chemical bond – mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together
Ionic Bonding-Being Like the Noble Gases All atoms want to have the same number of electrons as the Noble Gases. The Noble Gases have very stable electron configurations. In order to achieve the same electron configuration as the Noble Gases metal atoms will give up electrons to form positive ions (cations) and non-metal atoms will receive or take additional electrons to become negative ions (anions). IONS are charged particles. Al becomes Al+3 Na becomes Na+ Mg becomes Mg+2 Cl becomes Cl- O becomes O-2 N becomes N-3 The positive and negative ions are attracted to each other electrostatically.
Ionic Bonds • results from electrical attraction between large numbers of cations and anions • atoms donate or accept electrons from each other
Putting Ions Together Na+ + Cl- = NaCl Ca+2 + Cl- = CaCl2 Ca+2 + O-2= CaO Na+ + O-2 = Na2O Al+3 + S-2 = Al2S3 Ca+2 + N-3 = Ca3N2 You try these! Li+ + Br- = LiBr Mg+2 + F- = MgF2 Al+3 + I- = AlI3 (NH4)3PO4 NH4+ + PO4-3 = Not NH43PO4 Sr3P2 KCl Sr+2 + P-3 = K+ + Cl- =
Covalent Bonds • results from sharing of electron pairs between two atoms • the electrons shared belong to both atoms
Covalent Bonds • Polar Covalent when electrons are shared unevenly • Nonpolar Covalent when electrons are shared evenly
Ionic vs. Covalent • bonding usually does not fall in one category or the other, but somewhere in between • type of bond depends on the elements differences in electronegativities 0.3
Polarity • Polar- uneven distribution of charge • Show partial charges on structure by using (lowercase delta)
Practice • Determine whether each of the following bonds will be: ionic, polar covalent, OR nonpolar covalent
S and H 2.5-2.1=0.4 polar covalent S and Cs 2.5-0.7=1.8 ionic C and Cl 3.0-2.5=0.5 polar covalent Practice
Cl and Ca 3.0-1.0=2.0 ionic Cl and O 3.5-3.0=0.5 polar covalent Cl and Br 3.0-2.8=0.2 nonpolar covalent Practice
Patterns • What kind of patterns do you see? • metals + nonmetals = ionic • nonmetals + nonmetals = covalent