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frosja888 [35]
3 years ago
9

Which statements accurately describe Dmitri Mendeleev’s contributions to the development of the periodic table? Check all that a

pply.
Mendeleev wrote the first modern chemistry textbook.
Mendeleev produced the first orderly arrangement of known elements.
Mendeleev ordered the elements by increasing atomic number.
Mendeleev used patterns to predict undiscovered elements.
Mendeleev accounted for variations resulting from isotopes.
Chemistry
2 answers:
Varvara68 [4.7K]3 years ago
8 0

Answer:

  • <em><u>Mendeleev produced the first orderly arrangement of known elements.</u></em>

  • <em><u>Mendeleev used patterns to predict undiscovered elements.</u></em>

Explanation:

  • <u>Mendeleev produced the first orderly arrangement of known elements and used patterns to predict the undiscovered elements.</u>

        Those two statments are true.

For the time being there were some 62 known elements. Before Medeleev some schemes to order part of the elements were proposed, but Medeleev showed the relationship between the atomic mass and the properties of the elements (supports second choice). This arrangement is known as the periodic table.

More importantly, Mendeleev predicted correctly the existance and properties of unknown elements, which is his major contribution: he left blanket spaces which where gradually filled when new elements where discovered (this supports the fourth choice).

The first modern chemistry book was written by Antoine Lavoisier (this discards first option).

Mendeleev ordered the elements by increasing mass number (this discards third choice), which was corrected later by the scientist Henry Moseley, who ordered the elements by increasing atomic number (number of protons).

Isotopes were not known by Mendeleev times, so this discards the last option.

Delvig [45]3 years ago
4 0

Answer:

The answer is B and D

Explanation:

I just took the test and got it right.

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If you count the number of electrons (small dots), you have the atomic number. In this case you have 11 so this atom is a sodium atom. Sodium has 1 valence electron (electron on the outer shell) and chlorine has 7. This means that if sodium gave one electron away and chlorine would obtain one electron, they would both have the (ideal) noble gas conformation (full outer shell).
4 0
3 years ago
The molar mass of Cr(OH)2 is:
son4ous [18]

The molar mass of Cr(OH)_2 is 86.02 g/mole .

<h3><u> Explanation:</u> </h3>

The molar mass of a chemical compound is represented as the mass of a unit of that compound separated by the number of substances in that unit, measured in moles. The molar mass is a volume, not molecular, the property of a substance.

The molar mass is a percentage of various examples of the compound, which usually change in mass due to the appearance of isotopes.

From the below attached table, the Molar mass of Cr(OH)_2 is 86.0108 g/mol.

3 0
3 years ago
What would be the matching DNA strand for the code below?:
max2010maxim [7]

Answer:

D. TTACGCCAGG. that would be your answer.

4 0
2 years ago
Read 2 more answers
Question :What's oxidation?<br>​
professor190 [17]

Answer:

The process or result of oxidizing or being oxidized.(Rust)

Explanation:

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6 0
3 years ago
Suppose the half-life is 9.0 s for a first order reaction and the reactant concentration is 0.0741 M 50.7 s after the reaction s
bazaltina [42]

<u>Answer:</u> The time taken by the reaction is 84.5 seconds

<u>Explanation:</u>

The equation used to calculate half life for first order kinetics:

k=\frac{0.693}{t_{1/2}}

where,

t_{1/2} = half-life of the reaction = 9.0 s

k = rate constant = ?

Putting values in above equation, we get:

k=\frac{0.693}{9}=0.077s^{-1}

Rate law expression for first order kinetics is given by the equation:

k=\frac{2.303}{t}\log\frac{[A_o]}{[A]}     ......(1)

where,

k = rate constant  = 0.077s^{-1}

t = time taken for decay process = 50.7 sec

[A_o] = initial amount of the reactant = ?

[A] = amount left after decay process =  0.0741 M

Putting values in equation 1, we get:

0.077=\frac{2.303}{50.7}\log\frac{[A_o]}{0.0741}

[A_o]=3.67M

Now, calculating the time taken by using equation 1:

[A]=0.0055M

k=0.077s^{-1}

[A_o]=3.67M

Putting values in equation 1, we get:

0.077=\frac{2.303}{t}\log\frac{3.67}{0.0055}\\\\t=84.5s

Hence, the time taken by the reaction is 84.5 seconds

6 0
3 years ago
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