With newly discovered materials, nothing is yet know about them. Scientists don't know how to conduct physical/chemical experiments without damaging the element. Lethal substances or corrosive materials can be set off from combustion or decomposition. It would be difficult to determine the properties because no one knows what the element is made of. Chemical properties are often characterized by <span>reactivity with other chemicals, such as toxicity, coordination number, flammability, enthalpy of formation, the heat of combustion, and <span>oxidation states. It is difficult to measure those things when you have no idea what an element may be giving off. </span></span>

1eV --------- is ----------- 1.6*10⁻¹⁹J
1.931eV ---- is ----------- x
x = [1.931eV*1.6*10⁻¹⁹J]/1eV ≈ 3,1*10⁻¹⁹J
<u>ANSWER E</u>
12. F - Most of these elements are metals.
13. C - Ability to rust
Answer:
See detailed explanation.
Explanation:
Hello.
In this case, since the electron configuration of potassium whose atomic number is 19 turns out:

We can see that the last level is 4 which has one electron, meaning that potassium has one valence electron. Moreover, since bromine's atomic number is 35, its electron configuration is:

We can see that the last level is also 4 and it has 2+5 = 7 valence electrons. In such a way, we infer that the valence electrons are computed by the electrons at the outer or last energy level of an element.
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