12.3-12.5
Bond polarity and dipole moment
Dipole moment
-molecules that have a center of positive charge and a center of negative charge and is represented with an arrow
?Give an example of a diatomic molecule?
H2 or Br2 (true covalent) or HF(polar covalent)-do have unequal charges
-very critical that water is polar as it can surround and attract both positive and negative ion so that materials dissolve in water(universal solvent)AND polarity causes water molecules to be attracted to each other STRONGLY so it is hard to change water from a liquid to a gas(good thing so our oceans are not empty)
Stable electron configurations/ions charges
-metals lose enough electrons to achieve the configuration of the previous noble gas
?Give an example of a noble gas?
Argon
Na =[Ne]3s1 à [Ne]
(loses an electron)
-nonmetals gain enough electrons to achieve the configuration of the next noble gas
O=[He]2s22p4 à [Ne]
(gains two electrons)
-in almost all stable chemical compounds of the representative elements, all of the atoms have achieved a noble gas electron configuration
-in covalent bonds, two nonmetals react and share electrons in a way that completes the configuration for a noble gas
O=[He]2s22p4 à[Ne] (water)
(shares with 2 H atoms)
Predicting formulas of ionic compounds
-consider the valance electron configuration
-the more electronegative atom will receive the electrons
-they will need to complete a noble gas configuration
?Since chemical compounds are neutral, what are do their charges equal?
-chemical compounds are always neutral so their charges must = 0
Ca=[Ar]4s2à[Ar]
(loses 2e-)
O =[He]2s22p4à[Ne]
(gains 2 e-)
Ca+2O-2 is neutral
Ionic Compounds
?What are some characteristics of ionic compounds?
-metals react with nonmetals
-very stable-takes a lot of energy to break them apart
-high melting points
-strong attractions of positive and negative ions
-ions are packed like hard spheres where the smaller ions occupy the interstices(holes between the larger ions)
-cations is always smaller than the parent atom and the anion is always larger than the parent ions-cations lose electrons and anions gain electrons
?Why is this true?
the metal loses its electrons
-individual polyatomic ions are held together by covalent bonds