The atomic number corresponds to the number of protons
Protons are denoted as P and Electrons as E P = E
The atomic mass equals the sum of Neutrons and Protons
Atomic number = atomic mass = neutrons
P = E
Atomic mass - atomic number = Neutrons
Example:
Calcium consists of 20 Protons 20P = 20E
Atomic mass - atomic number = neutron count:)
Your Question: There are two kinds of elements that didn't appear on the periodic table until after 1892. What kinds are they and why do you think it took so long to discover them?
The Answer: The insights of Moseley led chemists to further refine the periodic table and uncover additional gaps, indicating that several new elements, specifically with atomic numbers 43, 61, 72, and 75, remained undiscovered. These elements were later identified as technetium, promethium, hafnium, and rhenium, respectively.
Explanation: Physicist Henry Moseley used x-rays to determine the atomic number of elements, which facilitated a more accurate organization of the periodic table. His life and the discovery of the correlation between atomic number and x-ray frequency, known as Moseley's Law, are significant to note.
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Answer:
710.33 g NO2
Explanation:
2 C8H18 + 25 O2 → 16 CO2 + 18 H2O
(800 g octane) / (114.2293 g C8H18/mol x (25/2)) = 87.54 mol O2 utilized for combusting octane
= 15.44 mol O2 used for generating NO2
O2 + 2NO → 2NO2
(15.44 mol O2) x (2/2) x (46.0056 g NO2/mol) = 710.33 g NO2
1) To express 0.89% m/v, it equals 0.89 grams of NaCl per 100 ml of solution.
This corresponds to 8.9 grams of NaCl in 1000 ml of solution, or 8.9 grams in 1 liter.
2) Molarity is represented as M = moles of solute / liters of solution.
Thus, we need to determine the moles in 8.9 grams of NaCl.
3) The molar mass of NaCl is calculated as 23.0 g/mol + 35.5 g/mol = 58.5 g/mol.
4) Therefore, the number of moles of NaCl calculates as mass / molar mass = 8.9 g / 58.5 g/mol = 0.152 moles.
5) Consequently, M = 0.152 moles of NaCl / 1 liter of solution = 0.152 M.
Answer: 0.152 M
