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Brrunno [24]
3 years ago
13

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

Chemistry
2 answers:
CaHeK987 [17]3 years ago
5 0
<span>If you give it a good search, the most used answer would probably be as follows,

</span><span>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.
</span>
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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One way to represent a substance is with a chemical formula. In the formula CO2, what do the symbols Cand o refer to?
olga2289 [7]

Answer:

C is for carbon and O is for oxygen

5 0
4 years ago
Read 2 more answers
Hamid made this table to organize his notes on the properties of acids and bases.
Molodets [167]

Answer : The property in the wrong column is, base form hydrogen gas with metals

Explanation :

Acid : It is a substance that has ability of donating a proton or hydrogen ion, H^+.

The properties of an acid are :

  • Acids are sour in taste.
  • It conduct electricity.
  • The texture of an acid solution is sticky.
  • It react with carbonates to give salt.
  • It changes the color of the litmus paper to red.
  • It react with a metal to give compound and hydrogen gas.

Base : It is a substance that has ability of donating hydroxide ion, OH^-.

The properties of an base are :

  • Base are bitter in taste.
  • It conduct electricity.
  • The texture of an base solution is slippery.
  • It changes the color of the litmus paper to blue.
  • It does not react with a metal.

Hence, from the above information, we conclude that the property in the wrong column is, base form hydrogen gas with metals .

8 0
3 years ago
Read 2 more answers
Calculate the mass of each sample.
Vsevolod [243]
1 mole of any substance has Avagadro number of molecules and it's weight is equal to its molecular weight.
.......................................................................................................................
Answer 1:
Molecular weight of HNO3 = 63.01 g/mol

Therefore, 1mole of HNO3 = 63.03 g
Hence, 15.7 mole of HNO3 = 63.03 X 15.7
                                            = 989.57 g

Thus, mass of 15.7 mole of HNO3 = 989.57 g
..........................................................................................................................
Answer 2: 
Molecular weight of H2O2 = 34.01 g/mol

Therefore, 1mole of H2O2  = 34.01g
Hence, 0.00104 mole of H2O2  = 34.01 X 0.00104
                                            = 0.03537 g

Thus, mass of 0.00104 mole of H2O2 is 0.03537 g
.........................................................................................................................
Answer 3: 
Molecular weight of SO2 = 64.07 g/mol

Therefore, 1mole of SO2 = 64.07 g
Hence, 72.1  mmole of SO2 = 64.07 X 0.0721
                                            = 4.619 g

Thus, mass of 72.1 mm of SO2 is 4.619 g
.........................................................................................................................
Answer 4:
Molecular weight of XeF2 = 169.29 g/mol

Therefore, 1mole of XeF2 = 169.29 g
Hence, 1.23 mole of XeF2 = 169.29 X 1.23
                                            = 208.23 g

Thus, mass of 1.23 mole of XeF2 is 208.23 g

8 0
4 years ago
A chemistry graduate student is given 125.mL of a 0.20M acetic acid HCH3CO2 solution. Acetic acid is a weak acid with =Ka×1.810−
Over [174]

Answer : The mass of sodium acetate is, 1.097 grams.

Explanation : Given,

The dissociation constant for acetic acid = K_a=1.8\times 10^{-5}

Concentration of acetic acid (weak acid)= 0.20 M

volume of solution = 125. mL

pH = 4.47

First we have to calculate the value of pK_a.

The expression used for the calculation of pK_a is,

pK_a=-\log (K_a)

Now put the value of K_a in this expression, we get:

pK_a=-\log (1.8\times 10^{-5})

pK_a=5-\log (1.8)

pK_a=4.74

Now we have to calculate the concentration of sodium acetate (conjugate base or salt).

Using Henderson Hesselbach equation :

pH=pK_a+\log \frac{[Salt]}{[Acid]}

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

4.47=4.74+\log (\frac{[Salt]}{0.20})

[Salt]=0.107M

Now we have to calculate the mass of sodium acetate.

\text{Concentration}=\frac{\text{Mass of }NaCH_3CO_2\times 1000}{\text{Molar mass of }NaCH_3CO_2\times \text{Volume of solution (in mL)}}

0.107M=\frac{\text{Mass of }NaCH_3CO_2\times 1000}{82g/mol\times 125mL}

\text{Mass of }NaCH_3CO_2=1.097g

Therefore, the mass of sodium acetate is, 1.097 grams.

6 0
4 years ago
A particular reaction, a → products, has a rate that slows down as the reaction proceeds. the half-life of the reaction is found
irga5000 [103]
Generally, the rate of a reaction will decrease with increasing temperature, although there are some exceptions in the case of non-elementary reactions. However it is more likely that the first statement is false.
Half-life is a measure of the time taken for a to reach 1/2 of its initial concentration, and is generally completely independent of reagent concentration within a first order reaction, which is likely what this reaction is, therefore statement 2 is also likely false.
Hope this helps!
8 0
4 years ago
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