The proper science is validated by Experimentation and Testing .
What is experiment and testing?
Experiment is performed to support or Refuge a hypothesis which is given by someone.
Test is to figure out what we expect and what we have observed.
So , the proper validation of science is Experiment and testing because science is all about hypothesis, discoveries if want to prove them right or wrong we have to perform experiment and test .
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Answer is: D. Cl (chlorine).
The ionization energy (Ei) is the minimum amount of energy required to remove the valence electron, when element lose electrons, oxidation number of element grows (oxidation process).
Barium, potassium and arsenic are metals (easily lost valence electrons), chlorine is nonmetal (easily gain electrons).
Alkaline metals (in this example, potassium) have lowest ionizations energy and easy remove valence electrons (one electron), earth alkaline metals (in this example, barium) have higher ionization energy than alkaline metals, because they have two valence electrons.
Nonmetals (in this example chlorine) are far right in the main group and they have highest ionization energy, because they have many valence electrons.
For example, at sea level the atmospheric pressure is 760 mm Hg<span> (also expressed as 760 torr, 101325 Pa, 101.3 kPa, 1013.25 mbar or 14.696 psi) and pure </span>water<span> boils at 100°C. However, in Calgary (approx. 1050m above sea level) the atmospheric pressure is approximately 670 </span>mm Hg<span>, and </span>water<span> boils at about 96.6°C.</span>
If you go backwards two elements, you will find Neon (Ne). If you go forwards six, you will find Argon (Ar). so the closest will be neon
