BONDING

1. A
NH4+ ion is formed by an NH3 molecules and an H+ ion, i.e. H3N→H+.
After NH4+ is formed, it exists as a cation with central N atom linking tetrahedrally to four H atoms by covalent bonds. The dative bond cannot be identified then.
A and B could be the answer, but A is a better one.


2. A
Across a period from Group I and Group VII (neglecting Group O due to its low reactivity), electronegativity is increasing. Across the period, the screening effect is nearly unchanged. The nuclear charge is increasing, and thus the bond pair of electrons experiences an increase in nuclear attraction.
Down a group, number of electron shells is increasing. The increase in nuclear charge is almost completely cancelled by the increase in screening effect. The bond pair of electrons experiences a decrease in nuclear attraction due to the increase in atomic size.


2007-01-07 19:40:24 補充：
Typing error : The answer for Q.2 is B.

1- C

2-C