Families boron

It will pay you to know (without having to look in the periodic table or tables of electron configurations) that the halogens (F, Cl, Br, I, At) all have seven valence electrons, that the oxygen family (O, S, Se, Te) all have six, that the nitrogen family (N, P, As) have five, that the carbon family (C, Si) have four, and that the boron family (B) have three It will also pay you to know that electronegativities decrease from right to left in a row, or from top to bottom in a column, in the periodic table... 

Examples of this kind are most often found in compounds of the boron family, group III of the periodic table. 

An additional hindrance to relating the reactivity of R M types to the electronic configuration of the metal involved is the tendency for extensive intermolecular associations of organometallic compounds. The extent to which alkyls of the boron family dimerize is a function of both the size and electric field of the metal atom. The reactivity of monomeric triethylborane versus that of dimeric triethylaluminum is therefore less readily analyzed into electronic effects. 

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