For each question below, there are two statements. Decide whether each statement is true or false. Then decide whether Statement II is a correct explanation for Statement I.
Statement I
Statement II
6. Every aluminum-27 atom has 27 protons BECAUSE The mass number of aluminum-27 is 27.
and 27 electrons.
7. Isotopes of an element have different BECAUSE The nuclei of an element's isotopes contain dif-
atomic masses.
ferent numbers of protons.
8. An electron is repelled by a negatively BECAUSE An electron has a negative charge.
charged particle.
9. In an atom, the number of neutrons is BECAUSE The mass number is generally equal to or
generally equal to or greater than the
greater than the atomic number.
number of protons.

most historians agree that gabriel mouton, the vicar of st. paul’s church in lyons, france, is the “founding father” of the metric system. he proposed a decimal system of measurement in 1670. mouton based it on the length of one minute of arc of a great circle of the earth (now called a nautical mile, 1852 meters). he also proposed the swing-length of a pendulum with a frequency of one beat per second as the unit of length (about 25 cm). a pendulum beating with this length would have been fairly easy to produce, thus facilitating the widespread distribution of uniform standards. over the years, his work was revised, improved, and extended by a number of french scientists.

the political sponsor of weights and measures reform in the french revolutionary national assembly was the bishop of autun, better known as talleyrand. under his auspices, the french academy appointed several committees to carry out the work of developing a usable system of weights and measures for france. one of the committees recommended a decimalized measurement system based upon a length equal to one ten-millionth of the length of a quadrant of the earth’s meridian (i.e., one ten-millionth of the distance between the equator and the north pole).