Chemistry Past Questions and Answers

Elements X and Y have electronic configurations 1s<sup style='font-size: smaller;'>2</sup>2s<sup style='font-size: smaller;'>2</sup>2p<sup style='font-size: smaller;'>6</sup> and 1s<sup style='font-size: smaller;'>2</sup>2s<sup style='font-size: smaller;'>2</sup>2p<sup style='font-size: smaller;'>6</sup>3s<sup style='font-size: smaller;'>2</sup>3p<sup style='font-size: smaller;'>1</sup> respectively. When they combine, the formula of the compound formed is

The atomic number of caesium is 55 and its atomic mass is 133. The nucleus of caesium atom therefore contains

Four elements P,Q, R and S have atomic numbers of 4, 10, 12 and 14 respectively . Which of these electrons is a noble gas?

How many valence electrons are contained in the element represented <sup style='font-size: smaller;'>31</sup><sub style='font-size: smaller;'>15</sub>P?

The gaseous pollutant sulphur (IV)oxide is most likely to be detected in fairly reasonable quantities in the area around a plant for the