Where are the substances?
This problem is providing some chemical formulas and the number and types of atoms are required according to them; thus, we proceed as follows:
<h3>Chemical formulas:</h3><h3 />
In chemistry, we define chemical formulas as expressions showing the types and number of atoms a substance has. The types of atoms are found across the periodic table and the number is defined by the subscripts appearing in the formula.
a. It should be Fe₂O₃ as iron(III) oxide and in such a case it will have two iron atoms and three oxygen atoms.
b. It is potassium permanganate and it has one atom of both manganese and potassium and four oxygen atoms.
c. It should be CH₄, methane, and in such a case, it will have one carbon atom and four hydrogen atoms.
d. It should be NH₄NO₃, ammonium nitrate, and in such a case it will have two nitrogen atoms, four hydrogen atoms and three oxygen atoms.
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Answer:

Explanation:
Hello,
The frequency and wavelength of electromagnetic waves propagating in free space might be related to each other by using the following equation:
c=λf
Solving for the frequency:
f=c/λ
Knowing that λ stands for the wavelength (642 nm for the mentioned incident light), c the light velocity (300.000 m/s) and f the frequency, we get the asked frequency as:
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In comparing two isotopes of the same element, the atomic number, stays the same.
Allow me to explain: The protons in an isotope ALWAYS stays the same, but the neutrons change. But, what's the atomic number made up of?
Protons, which means it won't change.
However, the atomic mass is made up of neutrons + protons, so only the atomic mass would change - not the atomic number.
Communication skills were developed so knowledge could be passed along to younger generations.
<h3>How knowledge will pass through generations?</h3>
Knowledge will pass from one generation to another with the help of education. The skill people give education to their youngers about fire and tools. In this way, skills of fire and tools pass from one generation to another.
So we can conclude that communication skills were developed so knowledge could be passed along to younger generations.
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