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cestrela7 [59]
3 years ago
6

There are two kinds of elements that didn't appear on the periodic table until after 1892. What kinds are they and why do you th

ink it took so long to discover them?
Chemistry
2 answers:
rosijanka [135]3 years ago
6 0

Answer:

The two elements are Argon and Helium .

They are noble gas  and are not reactive

Explanation:

The two kinds of element are argon and helium. These two element were discovered in 1892 by a Scottish chemist Williams Ramsay.

These two elements are known as noble gas or inert gas  because of how hard they find it to react with other elements.

Elements back then were discovered through their reactivity with other elements but It took so long to discover these elements(argon and helium) because of their unreactive nature . Combine with the fact that they were odorless, tasteless and colorless it was more hard to discover them.

Lelu [443]3 years ago
5 0

Your Question: There are two kinds of elements that didn't appear on the periodic table until after 1892. What kinds are they and why do you think it took so long to discover them?

The Answer: Moseley’s analysis enabled chemists to refine the table further  and reveal more gaps, which suggested that there were more new  elements waiting to be discovered, with atomic numbers 43, 61, 72  and 75. Scientists subsequently found these elements—now  known as technetium, promethium, hafnium and rhenium,  respectively.

Explanation: Physicist Henry Moseley discovered the atomic number of each element using x-rays, which led to more accurate organization of the periodic table. We will cover his life and discovery of the relationship between atomic number and x-ray frequency, known as Moseley's Law.

Remember to read study guides, lessons and notes to rely yourself on; key to success is working hard. Good Luck!

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You need to prepare a solution with a specific concentration of Na+Na+ ions; however, someone used the end of the stock solution
babymother [125]

Explanation:

Ionic equation

NaCl(aq) --> Na+(aq) + Cl-(aq)

Na2SO4(aq) --> 2Na+(aq) + SO4^2-(aq)

In NaCl solution, 1 mole of Na+ is dissociated in 1 liter of solution while in Na2SO4, 2 moles of Na+ is dissociated in 1 liter of solution.

Molecular weight of NA2SO4 = (23*2) + 32 + (16*4)

= 142 g/mol

Molecular weight of NaCl = 23 + 35.5

= 58.5 g/mol

Masses

% Mass of NA+ in Na2SO4 = mass of Na+/total mass of Na2SO4 * 100

= 46/142 * 100

= 32.4%

% Mass of NA+ in NaCl = mass of Na+/total mass of NaCl * 100

= 23/58.5 * 100

= 39.3%

Therefore, the % mass of Na+ in NaCl and Na2SO4 are different so it cannot be used.

7 0
3 years ago
Thermal energy always moves from a greater energy level to a lesser energy level
Nookie1986 [14]

Answer:

\fbox{Law -Based \: on \: laws \: of \: thermodynamic}

Explanation:

At constant pressure Thermal energy always moves from a greater energy level to a lesser energy level, laws of thermodynamics prove that.

Nature always likes to attain equilibrium either it's movement of heat energy or flow of water from higher region to lower region. The first and second law of thermodynamics are profe of that, the first law says that the total energy of universe is Constant. Energy can not be destroyed it always changes from one form to another, by work and heat. The second law explains why thermal energy moves from a greater energy level to a lesser energy level, it deals with the change in entropy of a system and surrounding and states heat flows from hot environment to cold environment.

<em><u>Thanks for joining brainly community!</u></em>

6 0
2 years ago
The theater student talks about a type of theater from Japan called ___________.
TiliK225 [7]
I think the correct answer would be Kabuki. It is a Japanese traditional form of theater that is characterized by the heavy make-up worn by the performers. It started during the Edo Period. It is one of the major classical theater in Japan.
8 0
3 years ago
Sound usually travels most rapidly in
Mariana [72]
Sounds travels most rapidly in solid objects, especially those that are dense. These objects have closely packed atoms, and energy that is traveling in vibrations (the sound) can easily pass between the touching atoms.
4 0
3 years ago
A gas with an empirical formula C2H2O has a molecular weight of 120.6g/mol. A possible molecular formula for the gas is
Virty [35]

M(C2H2O)= 12.0*2 +1.0*2 +16.0 = 42 g/mol is a molar mass for empirical formula.

120.6g/mol/42g/mol ≈ 3

So, empirical formula should be increased 3 times,

and molecular formula is C6H6O3.

Answer is D.

7 0
3 years ago
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