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Physical Science 18
| Question | Answer |
|---|---|
| Octet rule | atoms are less stable without valence electrons, so they have a tendency to bond to fill their outer level with 8 electrons |
| Chemical bond | force that holds atoms together by sharing, gaining, or losing electrons (how atoms pair up to help complete the 8 valence electrons) |
| Electronegativity | ability to attract and hold electrons when bonded to other atoms (related to electron affinity; based on fluorine) |
| Low electronegativity | metals; few valence electrons |
| High electronegativity | nonmetals; almost 8 valence electrons |
| Electronegativity helps us determine | the types of atoms which will bond and what type of bond they will form |
| Covalent | share electrons; usually between nonmetals |
| Ionic | gain or lose electrons; usually between metals and nonmetals |
| Metallic | “share” electrons; usually between metals |
| Numbered subscripts | how many of each atom is bonded |
| Covalent bonds | force of attraction formed as a result of sharing electrons; elements share electrons molecules; exists only between two atoms |
| Polyatomic molecules | more than two atoms covalently bonded |
| Properties of covalent bonds | not as strong as ionic bonding; low melting point; gases or liquids in standard conditions(some solids); melt or decompose at a low temperature; not good conductors |
| Polarity | determined by the difference in attraction for the electrons between the atoms covalently bonded; difference in electronegativity between bonded elements |
| Nonpolar | no difference between electro negativities; only diatomic molecules of the same elements; equally shared |
| Polar | large difference in electronegativities; unequally shared |
| Ionic | attraction formed between oppositely charged ions in an ionic compound; big EN; electrons play favorites; gain or lose electrons; opposites attract |
| Cation | positive ion |
| Anion | negative ion |
| Properties of ionic bonds | solids at room temperature; high melting points; dissolve in water; good conductor |
| Metallic bonds | positive metal ions immersed in a sea of negative electrons |
| Properties of metallic bonds | solids at room temperature; malleability(can be hammered); ductility(ability to be made into wire); good conductors of heat and electricity; shiny luster |