Answer:
B, C
Explanation:
The Lewis dot structures that are valid are for B and C.
Regarding A;
The Lewis representation of carbon is correct. Each of the four dots symbolizes the four valence electrons.
However, the nitrogen with a single dot above, to the left, and below and a -3 charge isincorrect. For it to have a -3 charge, it must possess 8 Lewis dots (two on each side).
The nitrogen showing four dots (on top, right, bottom and left) is incorrect.
In B;
An oxygen having two dots positioned above and below with one dot on both sides is correct , as the 6 dots indicate oxygen's valence electrons.
In C;
A carbon shows two dots at each position and has a charge of +4. This is correct because the charge reflects that it has gained four electrons giving it 8 valence electrons.
In D;
An oxygen shows two dots above, to the left and below, with a charge of -2. This is incorrect as not all Lewis dots are present. Two are missing.
Answer:
Explanation:
The relationship between the new temperature scale and the absolute temperature scale is defined as follows
Aw = 2 K
for K = 273.15 (the freezing point of water on the absolute scale)
Aw = 2 x 273.15 = 546.3 K
Each division of the new scale is equivalent to half that of each division on the absolute scale
each division of the new scale is minimal.
The value of R = 8.314 J per mole per K
Here, per K corresponds to 2Aw
Hence, the value of R in the new scale = 8.314/2 J per mole per Aw
= 4.157 J per mole per Aw
k = R / N
= 4.157 / 6.02 x 10²³
= .69 x 10⁻²³
= 6.9 x 10⁻²⁴ J per molecule per Aw .
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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