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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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GenaCL600 [577]

The change of the statue of liberty from copper to green is an example of a chemical change.

<h3>Physical and chemical change</h3>

A physical change does not involve the formation of new substances and the composition of the substance does not change. However, in a chemical change, a new substance is formed and the composition of the substance changes.

The statement that reflect a chemical change is;

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Learn more about physical and chemical change: brainly.com/question/13316655

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2 years ago
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3 years ago
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How many grams of material is lost in the aqueous phase if two extractions are carried out on 100 mL of a 5% (m/v) aqueous solut
san4es73 [151]

Answer:

4.94g of material

Explanation:

Partition coefficient (Kp) of a substance is defined as the ratio between concentration of organic solution and aqueous solution, that is:

Kp = <em>8 = Concentration in Ethyl acetate / Concentration in water</em>

100mL of a 5% solution contains 5g of material in 100mL of water. Thus:

8 = X / 100mL / (5g-X) / 100mL

<em>Where X is the amount of material in grams that comes to the organic phase.</em>

8 = X / 100mL / (5g-X) / 100mL

8 = 100X / (500-100X)

4000 - 800X = 100X

4000 = 900X

4.44g = X

<em>Thus, in the first extraction you will lost 4.44g of material from the aqueous phase.</em>

And will remain 5g-4.44g = 0.56g.

In the second extraction:

8 = X / 100mL / (0.56g-X) / 100mL

8 = 100X / (56-100X)

448 - 800X = 100X

448 = 900X

0.50g = X

<em>In the second extraction, you will extract 0.50g of material</em>

Thus, after the two extraction you will lost:

4.44g + 0.50g = <em>4.94g of material</em>

<em></em>

6 0
3 years ago
Convert 15.6 g Na2Cr2O7 to moles of Na2Cr2O7.
Leviafan [203]

Answer:

261.96754

Explanation:

3 0
3 years ago
What is mass????????????????????
lbvjy [14]

Answer:

Do you need the definition or the equation to find it?

Explanation:

Equation:

Mass=volume x density

4 0
3 years ago
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