The periodic table has undergone some changes since it was first introduced. List three ways the modern periodic table differs from the one first published by Mendeleev in 1869.I have two of the three ways:
1: updating the atomic weight
2: adding newly discovered elements
However, I cannot come up with a last way the modern periodic table differs from Mendeleev's. Please help (:
Answers
According to the mendeleev tables that I looked up, hydrogen is catorgrized as a group I element, along with Lithium, sodium, Potassium etc. However, nowadays, hydrogen does not belong to any groups in the periodic table. This is because there are arguments about whether hydrogen belongs to group I. Group I elements are all alkali metals, while hydrogen is not. However, some people says that hydrogen only have one outer shell electron so it should be in group I. Some people even say hydrogen should belong to group VII because it only needs one more electron in order to achieve the duplet of electrons.
Therefore as you may notice, hydrogen in modern periodic tables are put in the center of the periodic table on the top.
Final answer:
The modern periodic table differs from Mendeleev’s original version in three main ways: it includes updated atomic weights, has been expanded to include newly discovered elements, and arranges elements by atomic number rather than atomic weight.
Explanation:
The modern periodic table of elements indeed differs in several key ways from the original 1869 version developed by Dmitri Mendeleev. Firstly, as you've noted, it has been updated to include the correct atomic weights of elements. Secondly, it has been expanded to include all of the newly discovered elements that weren't known in Mendeleev's time. And thirdly, elements on the modern periodic table are now arranged according to their atomic number (the number of protons in an atom's nucleus), rather than their atomic weight as was initially the case with Mendeleev's version. This change reflects a deeper understanding of atomic structure that has developed since the 19th century.
Learn more about Modern Periodic Table here:
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The diagram below illustrates a chemical equation. Chemical equations can be used to model chemical changes and show how elements become rearranged during chemical reactions. Which statement about is chemical equation is true? A. Two compounds have reacted to produce one compound. B. Two elements have reacted to produce one element. C. One compound and one element have reacted to produce one compound. D. Two elements have reacted to produce one compound.
1.5 mol H20
2.5 mol H20
O 3.5 mol NO2
O 1.0 mol NO2
Answers
Answer:
3.5 moles of NO2.
Explanation:
The balanced equation for the reaction is given below:
3NO2 + H2O —> NO + 2HNO3
Next, we shall determine the excess reactant. This is illustrated below:
From the balanced equation above,
3 moles of NO2 reacted with 1 moles H2O.
Therefore, 6.5 moles of NO2 will react with = (6.5 x 1)/3 = 2.17 moles of H2O.
From the above calculations, we can see that it will take a higher amount i.e 2.17 moles than what was given i.e 1 mole of H2O to react completely with 6.5 moles of NO2.
Therefore, NO2 is the excess reactant and H2O is the limiting reactant.
Next, we shall determine the number of mole of the excess reactant that reacted in the reaction. This is illustrated below:
From the balanced equation above, we can see that 3 moles of NO2 reacted with 1 mole of H2O.
Finally, we shall determine the leftover mole of the excess reactant after the reaction. This is illustrated below:
Given mole of NO2 = 6.5 moles
Reacted mole of NO2 = 3 moles
Leftover mole of NO2 =...?
Leftover mole = Given mole – Reacted mole
Leftover mole of NO2 = 6.5 – 3
Leftover mole of NO2 = 3.5 moles.
Therefore, 3.5 moles of NO2 remained after the reaction.
Answers
Answers
Hey there!
Given the reaction:
P4 + 10 Cl2 ------------------ 4 PCl5
Molar mass P4 = 124 g/mol
Number of moles P4:
n = mass of solute / molar mass
n = 24.0 / 124
n = 0.1935 moles of P4
Therefore:
1 mole P4 --------------- 4 moles PCl5
0.1935 moles P4 ------- moles PCl5
moles PCl5 = 0.1935 * 4
= 0.774 moles of PCl5
Hope that helps!
Answers
(AHC H20(I) = -285.8 kJ/mol)
A -120.9 kJ
B-241.8 kJ
C-571.6 kJ
D-285.8 kJ
Answers
Answer:
The heat of reaction when hydrogen and oxygen combine to form water is :
C. 571.6 kJ
Explanation:
Enthalpy Change = The enthalpy change for the formation of 1 mole of the substance from their standard state is called the enthalpy of formation.
This is intensive quantity as it is fixed for 1 mole .
Intensive properties = Those properties which are independent on the amount of the substance are intensive properties.
The value of these quantities does not get halve if you divide the substance into two equal parts. example , density, refractive index.
However , the enthalpy of reaction is extensive. Because on increasing the amount the value of the enthalpy also get doubles
Hence for this reaction :
Its value is -285.8 kJ for 1 mole
And here two moles are present . so the value of molar enthalpy is:
-285.8 x 2 = -571.6 kJ