CHM103 Class Notes Week 5 (9/199/23)
________________________________________________________________________________ From previous sections
Periodic Table, Characteristics of Different Groups, Electron Configuration ________________________________________________________________________________ Chapter 3: Ionic Compounds
Alkali metals (group 1A) form compounds with halogens (group 7A) Properties of these compounds include:
High melting points
Stable, white, crystalline solids
Soluble in water
Conduct electricity when dissolved in water
* Electricity can only flow through a medium containing
charged particles (ions) that are free to move
An ion is formed when a neutral atom gains or loses electrons Don't forget about the age old question of How much photosynthate is used for storage as
sucrose/starch and how much is metabolized?
The loss of electron(s) gives a positively charged ion called a cation
The gain of electron(s) gives a negatively charged ion called an anion
Positive charge =n+; Negative charge =n(which n is any integer)
3.2 Ions and the Octet Rule Don't forget about the age old question of How have the english common law influenced the american criminal justice system?
We also discuss several other topics like What regulates the synthesis of galactosidase?
Octet rule: Main group elements tend to undergo reactions that leave them with eight valence electrons
E.g. Alkali metals with a single valence electron react with halogens with seven valence electrons, giving both ns2np6 configurations with eight valence electrons (i.e. noble gas electron configuration)
E.g. N: 1s22s22p3 → N3: 1s22s22p6 We also discuss several other topics like When did chloroplasts evolve from cyanobacteria?
3.3 Ions of Some Common Elements
Transition metals form cations, but they can lose one or more d electrons in addition to losing valence s electrons. The octet rule is not followed. Metals form cations by losing one or more electrons Don't forget about the age old question of What is meant by a consensus decision?
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Reactive nonmetals form anions by gaining one or more electrons to achieve a noble gas configuration
Group 8A elements (noble gases) are unreactive
Ionic charges of main group elements can be predicted using the group number and the octet rule
E.g. 1A = X+, 2A = X2+
E.g. 5A = X3, 6A = X2, 7A = X