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
Don't forget about the age old question of What is the process by which molecules spread from high concentration to low concentration?
An ion is formed when a neutral atom gains or loses electrons
The loss of electron(s) gives a positively charged ion called a cation We also discuss several other topics like Why are obligations under civil code juridical necessity?
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
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) Don't forget about the age old question of What does the word "phagocytosis" mean in medical terms?
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E.g. N: 1s22s22p3 → N3: 1s22s22p6
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
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+ Don't forget about the age old question of What is the process of being socialized to a particular culture called?
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E.g. 5A = X3, 6A = X2, 7A = X