Answer:
B. using efficient light bulbs
The elements are placed in specific places on the periodic table based on their atomic number and outer electronic configuration which gives them certain properties.
The elements of same groups have same number of valence electrons.
Group 1: one electron in valence shell
Group 2: two electrons in valence shell.
Helium has only two electrons in its outer shell and it is grouped with elements that have completely filled outer orbitals, noble gas.
<span>During a nuclear reaction, an atom must emit an alpha particle, which consists of 2 protons (positively charged) and 2 neutrons (neutrally charged). Thus, the alpha particle has a charge of +2 (there are no electrons, which are negatively charged, to balance out the two protons). When an atom emits an alpha particle, it will lose this particle, thus losing 2 protons and 2 neutrons as well. Since the atom in the equation goes from 84 protons to 82, and 86 neutrons to 84, it lost 2 protons and 2 neutrons, indicating that it emitted an alpha particle.</span>
