Chemistry 2 Marks Questions

Nuclear charge is defined as the net positive charge experienced by an electron in the orbital of a multi-electron atom. The closer the orbital, the greater is the nuclear charge experienced by the electron (s) in it.
1. 2 s is closer to the nucleus than 3 s . Hence 2 s will experience larger effective nuclear charge.
2. 4 d will experience greater nuclear charge than 4 f since 4 d is closer to the nucleus than 4 f .
3. 3p will experience greater nuclear charge since it is closer to the nucleus than 3 f because 3 p is closer to nucleus than 3 f .

(iii) and (iv) show cis-trans isomerism. In structures (i) and (ii), two identical groups are attached to one of the doubly bonded carbon atoms.

1. The least precise term has 3 significant figures (i.e. in 0.112 ). Hence, the answer should have 3 significant figures.
2. Leaving the exact number (5), the second term has 4 significant figures. Hence, the answer should have 4 significant figures.
3. In the given addition, the least number of decimal places in the term is 4 . Hence, the answer should have 4 significant figures.

Electronegativity is directly related to the non - metallic character of elements.
Therefore, the rise in electronegativities across the period is followed by an increase in non - metallic properties of elements. Consequently, the decrease in electronegativities down the group is accompanied by an decrease in non - metallic properties of elements.