Answer:
J.J.Thomson discovered negatively charged particles by cathode ray tube experiment in the year 1897. The particles were name electrons.
Answer:
The two valid principles are:
- Scientific theories can be replaced by better theories.
- An experiment can disprove a theory that scientists have accepted.
Explanation:
The scientific knwoledge is not inmutable; it may (and does) change with new discoveries.
In fact, scientific theories cannot be proved right, instead they are constantly tested to try to disprove them. This is what the principle that theories are falsiable means.
As long as a scientific theory is not disproved it remains valid, but new discoveries may lead, eventually, to its disprovement.
Scientific knowledge evolves because new procedures, new technologies, and new evidence leads to a better understanding and better explanations.
Answer:
1.The metalloids; boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), polonium (Po) and astatine (At) are the elements found along the step like line between metals and non-metals of the periodic table.
2.hydrogen
The elements generally classified as nonmetals include one element in group 1 (hydrogen);
3.element iron
The element iron is in group 8, and therefore has two or three apparent valence electrons.
The people of Finland, who are secluded to some degree from the rest of the world by water, develop certain diseases due to the lack of genetic material from other ethnicities and races.
Physical barriers prevent fish from one stream from mating with fish from another stream, leading to a less varied gene pool among those fish. As time passes, the fish become unable to successfully mate with other groups.
A mountain range prevents two types of goat from mating, causing the gene pool to become less varied.<span>
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