Passage IV
Atomic nuclei can be represented by the combination of symbols
where Z is the number of protons in a nucleus of Element X, and A (equal to Z plus the number of neutrons) is the mass number of the same nucleus. For example, 
represents a nucleus of carbon containing 6 protons and 6 neutrons;
represents a nucleus of a different isotope (type) of carbon that contains 6 protons and 8 neutrons.
Atomic nuclei undergo 3 types of radioactive decay. Particles emitted during the 3 types of decay are listed in Table 1. Figure 1 shows a sequence of radioactive decays, called the uranium series, that begins with the decay of 
.
20. Based on Figure 1, if a nucleus of 
underwent beta decay, which of the following nuclei would be produced?
Your Answer is
Correct Answer is G
Explanation
It can be seen from table 1 that after beta decay occurs, the proton number Z increases by 1, while the mass number A remains unchanged. So the proton number (lower left corner) of the element appearing in the question stem becomes 91, and the mass number (upper right corner) is still 230