Answer:
About 60.
Explanation:
Mendeleev knew of 63 elements. He wrote their properties on cards and arranged them in order of atomic mass.
That's how he discovered that the properties of elements are periodic functions of their atomic masses.
Answer:

Explanation:
Hello,
In this case, we need to remember that for the required time for a radioactive nuclide as radium-226 to decrease to one half its initial amount we are talking about its half-life. Furthermore, the amount of remaining radioactive material as a function of the half-lives is computed as follows:

Therefore, for an initial amount of 100 mg with a half-life of 1590 years, after 1000 years, we have:

Best regards.
13.8 moles of carbon = 12 g/mol*13.8 or 165.6 grams
165.6 grams/ 2.26 g/mL = 73.27434 or 73.3 mL
I hope this helps!!!!
The new pressure would be = 4.46 atm
<h3>Further explanation</h3>
Given
V₁=6.7 L(at STP, 1 atm 273 K)
V₂=1.5 L
Required
The new pressure
Solution
Boyle's Law
At a constant temperature, the gas volume is inversely proportional to the pressure applied

P₂ = (P₁V₁)/V₂
P₂ = (1 atm x 6.7 L)/1.5 L
P₂ = 4.46 atm
Answer:
n=N/Na
n = \frac{8.23 \times {10}^{22} }{6.02 \times {10}^{23} } = 0.1367 \: mol
answer: 0.14 mol
Explanation: