Passage IV
Table 1 lists data about metal elements arranged in order of increasing atomic number (the number of protons contained in one atom). The melting point is the temperature at which a solid metal liquefies. An electrically neutral atom has an equal number of protons (positively charged particles) and electrons (negatively charged particles). A positive ion is formed when an atom loses one or more electrons. The first ionization energy is the energy that removes one electron from the neutral atom to form a＋1 ion. The atomic radius and ionic radius indicate the size of the neutral atom and of the +2 ion, respectively.
21. Which element would require the LEAST amount of energy to form a+1 ion?
Your Answer is
Correct Answer is A
Explanation
According to the reciprocal 3 and 4 lines in the text, it can be found that the first ionization energy is the energy that makes an atom into a +1 ion in the title, and the smallest Sc is 631 kJ, so choose A< /p>