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3 years ago

How did Henry Moseley revise Mendeleev's periodic table? (Please answer A.S.A.P.)

2 answers:

5 0

If you give it a good search, the most used answer would probably be as follows,

In 1914 Henry Moseley found a relationship between an element's X-ray wavelength and its atomic number (Z), and therefore rearranged the table by nuclear charge / atomic number rather than atomic weight. Before this discovery, atomic numbers were just sequential numbers based on an element's atomic weight. Moseley's discovery showed that atomic numbers had an experimentally measurable basis.

Hope this helps!

jekas [21]3 years ago

5 0

Answer:

Arranged the elements on the table in order of increasing number of protons, or atomic number.

Explanation:

Mendeleev listed the known chemical elements in ascending order of atomic mass. However, such classification gave some problems to Mendeleev's table, which was characterized by the impression that some elements appeared to be out of place. An example was argon which, when isolated, did not appear to have the correct mass to justify its position. Its relative atomic mass of 40 is the same as that of calcium, but these differed considerably: while argon is an inert gas, calcium is a very reactive metal.

In the early twentieth century, when Henry Moseley examined the x-ray spectrum of the elements, he found that all atoms of the same chemical element had the same nuclear charge, and therefore had the same number of protons, which consist of the atomic number of the elements. It was quickly concluded that the elements would be in an even more regular pattern when arranged in a table in ascending order of their atomic number rather than atomic mass.

Thus, we can conclude that Moseley revised Mendeleev's periodic table by arranging the elements on the periodic table in ascending order of proton number or atomic number.

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calculate the heat required in joules to convert 18.0 grams of water ice at a temperature of -20 c to liquid water at the normal

KIM [24]

Answer:

Explanation:

Heat required to convert ice to ice at 0⁰C

= mass x specific heat x rise in temperature

= 18 x 2.09 x 20

= 752.4 J .

heat required to convert ice at 0⁰C to water at 0⁰C

mass x latent heat of fusion

= 18 x 336

= 6048 J

Heat required to increase the temperature of water to 100⁰C

= 18 x 4.2 x 100

= 7560 J

Total heat required

7560 + 6048 + 752.4

= 14360.4 J

7 0

3 years ago

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vova2212 [387]

Answer:

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2 years ago

There are four substances, A, B C and D. A and C are pure substances. They cannot be broken down into anything simpler by chemic

yarga [219]

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3 years ago

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dem82 [27]

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3 years ago

14. 60. g of NaOH is dissolved in enough distilled water to make 300 mL of a stock solution. What volumes of this solution and d

zepelin [54]

The question is incomplete, the complete question is attached below.

Answer : The volumes of stock solution and distilled water will be, 20 mL and 80 mL respectively.

Explanation : Given,

Mass of NaOH = 60 g

Volume of stock solution = 300 mL

Molar mass of NaOH = 40 g/mol

First we have to calculate the molarity of stock solution.

$\text{Molarity}=\frac{\text{Mass of }NaOH\times 1000}{\text{Molar mass of }NaOH\times \text{Volume of solution (in mL)}}$

Now put all the given values in this formula, we get:

$\text{Molarity}=\frac{60g\times 1000}{40g/mole\times 300mL}=5mole/L=5M$

Now we have to determine the volume of stock solution and distilled water mixed.

Formula used :

$M_1V_1=M_2V_2$

where,

$M_1\text{ and }V_1$ are the molarity and volume of stock solution.

$M_2\text{ and }V_2$ are the molarity and volume of diluted solution.

From data (A) :

$M_1=5M\\V_1=20mL\\M_2=1M\\V_2=?$

Putting values in above equation, we get:

$5M\times 20mL=1M\times V_2\\\\V_2=100mL$

Volume of stock solution = 20 mL

Volume of distilled water = 100 mL - 20 mL = 80 mL

From data (B) :

$M_1=5M\\V_1=20mL\\M_2=1M\\V_2=?$

Putting values in above equation, we get:

$5M\times 20mL=1M\times V_2\\\\V_2=100mL$

Volume of stock solution = 20 mL

Volume of distilled water = 100 mL - 20 mL = 80 mL

From data (C) :

$M_1=5M\\V_1=60mL\\M_2=1M\\V_2=?$

Putting values in above equation, we get:

$5M\times 60mL=1M\times V_2\\\\V_2=300mL$

Volume of stock solution = 60 mL

Volume of distilled water = 300 mL - 60 mL = 240 mL

From data (D) :

$M_1=5M\\V_1=20mL\\M_2=1M\\V_2=?$

Putting values in above equation, we get:

$5M\times 60mL=1M\times V_2\\\\V_2=300mL$

Volume of stock solution = 60 mL

Volume of distilled water = 300 mL - 60 mL = 240 mL

From this we conclude that, when 20 mL stock solution and 80 mL distilled water mixed then it will result in a solution that is approximately 1 M NaOH.

Hence, the volumes of stock solution and distilled water will be, 20 mL and 80 mL respectively.

5 0

3 years ago