Imagine an element that has 15 protons, 16 neutrons, and 18 electrons. Which of the following would NOT be considered an isotope of this element? * 15 protons, 16 neutrons, and 15 electrons
15 protons, 17 neutrons, and 15 electrons
15 protons, 15 neutrons, and 18 electrons

A: 15 protons, 16 neutrons, and 15 electrons

Explanation: An isotope of an element is when neutrons are taken away from the nucleus, or added to the nucleus.  

If you change the amount of protons in the nucleus, not only will the charge become positive due to their being one more proton than an electron, but the atom will change to a new element, Sulfur. If you change the electron count, that will just affect how prominent the negative charge is on the atom, whether it be more negative by adding an electron, or more postitive by removing an electron. Therefore, the amount of neutrons that you add to the nucleus of an atom, will change the isotope of the atom, and that's why the answer is A because every other answer changes the neutron count other than A.  

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).

a electronegativity decreases beacuse the size of nucleus is bigger.