Imagine you are given a mystery element. It is, however, a discovered and known element. You may perform a maximum of two observ
ations or tests to determine its identity. Time and money is critical, so you need to prioritize your tests. If you can identify the mystery element with a single test, you get 100 super-geek points from your research lab team.
Pick two tests and justify why you think they will identify the mystery element with certainty. If you think the first test will be enough, explain why.
Choose from these available tests:
• classification into metal, nonmetal, or metalloid
• count of valence electrons
• count of electron shells
• atomic radius (error range: +/- 1 pm)
• electronegativity (error range: +/- 0.1)
• first ionization energy (error range: +/- 10 kJ/mole)
• melting point (error range: +/- 10 C)
• boiling point (error range: +/- 20 C)
Pick two tests and justify why you think they will identify the mystery element with certainty. If you think the first test will be enough, explain why.
Choose from these available tests:
• classification into metal, nonmetal, or metalloid
• count of valence electrons
• count of electron shells
• atomic radius (error range: +/- 1 pm)
• electronegativity (error range: +/- 0.1)
• first ionization energy (error range: +/- 10 kJ/mole)
• melting point (error range: +/- 10 C)
• boiling point (error range: +/- 20 C)
2 answers:
Answer:
Count of Valence electron followed by electron shells
Explanation:
The periodic table has certain very unique properties that help identify the elements.
The number of valence electrons in any element can be determined by the placement of the element in the group. An element from group III will have three valence electrons.
Hence, this test will help locate the group of the element in question.
This test should be followed by the number of electron shells.
In the Periodic table, the placement of any element in the row depends on the number of electron shells. An element from row II will have two electron shell.
These two tests will work like coordinates on the Periodic Table.
For example, the result is Group II, Row 3 is Calcium.
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Answer:
Approximately formula units (
).
Explanation:
Refer to a modern periodic table for the relative atomic mass of magnesium () and chlorine (
):
:
.
:
.
In other words, the mass of of
atoms would be (approximately)
.
Likewise, the mass of of
atoms would be approximately
.
One formula unit of the ionic compound includes exactly as many atoms as there are in the given formula. The formula mass of a compound is the mass of
of the formula units of this compound.
The formula includes one
atom and two
atoms.
Hence, every formula unit of would include the same number of atoms: one
atom and two
atoms. There would be
of
atoms and
of
atoms in
of
formula units.
Thus, the mass of of
formula units would be equal to the mass of
of
atoms plus the mass of
of
atoms. (The mass of
of each atom could be found from the relative atomic mass of each element.)
.
In other words, the formula mass of is
.
Therefore, the number of formula units in of
would be:
.
Multiple by Avogadro's Number
to estimate the number of formula units in
:
.