Answer: Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.
Explanation:
Dalton's Atomic Theory was proposed in the 20th century by an English Scientist named John Dalton. His theory is postulated as follows:
1) All elements are composed of tiny indivisible particles called atoms.
2) The atoms of any one element are identical to those of any other element. 3) Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds.
However, the final option is NOT one of Dalton's Theory
Answer:
12.213 minutes will be taken for 120 g-Thalium-208 to decay to 75 grams.
Explanation:
Radioactive isotopes decay exponentially in time, the mass of the isotope (
), in grams, is described by the formula in time (
), in minutes:
(1)
Where:
- Initial mass of the isotope, in grams.
- Time constant, in minutes.
In addition, the time constant associated with the isotope decay can be described in terms of half-life (
), in minutes:
(2)
If we know that 
, 
and 
, then the time taken by the isotope is:
12.213 minutes will be taken for 120 g-Thalium-208 to decay to 75 grams.
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❖ The correct answer choice is C. Natural selection usually causes a species to change gradually.
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The graph above represents a synthesis reactions in which two substances come to together to form one compound by releasing heat energy!
hope that helps! :))
