Answer:
- <em><u>Mendeleev produced the first orderly arrangement of known elements.</u></em>
- <em><u>Mendeleev used patterns to predict undiscovered elements.</u></em>
Explanation:
- <u>Mendeleev produced the first orderly arrangement of known elements and used patterns to predict the undiscovered elements.</u>
Those two statments are true.
For the time being there were some 62 known elements. Before Medeleev some schemes to order part of the elements were proposed, but Medeleev showed the relationship between the atomic mass and the properties of the elements (supports second choice). This arrangement is known as the periodic table.
More importantly, Mendeleev predicted correctly the existance and properties of unknown elements, which is his major contribution: he left blanket spaces which where gradually filled when new elements where discovered (this supports the fourth choice).
The first modern chemistry book was written by Antoine Lavoisier (this discards first option).
Mendeleev ordered the elements by increasing mass number (this discards third choice), which was corrected later by the scientist Henry Moseley, who ordered the elements by increasing atomic number (number of protons).
Isotopes were not known by Mendeleev times, so this discards the last option.
<h3>
Answer: D) all of the above</h3>
Explanation:
The lungs pump oxygen in and carbon dioxide out, which goes through the blood stream to help with the cell's energy needs.
Nutrients pass through the blood stream as well. The nutrients start with the digestive system (mouth, esophagus, stomach, small intestine) before going into the blood stream. The nutrients are building blocks to help make new cells when old ones die off.
When those cells die off, the body sheds them like dead skin, but internal dead cells are passed off as waste. This waste and other byproducts the body doesn't need passes through the blood stream as well.
In short, the blood stream is basically the highway to help get desired materials (eg: oxygen and nutrients) and get rid of waste (eg: carbon dioxide and other unwanted byproducts or dead cell material)
So that's why the answer includes A, B and C.
Answer: B
Explanation: A fluorine atom has nine protons and nine electrons, so it is electrically neutral. (neutral =0)
A
Explanation:
The coiling up of DNA with the help of histone proteins - to what is called heterochromatic regions- is part of gene regulation. This makes genes inaccessible to RNA polymerase that makes mRNA from the genes. When the genes are exposed by DNA unwinding, these genes are transcribed and the resulting mRNAs are translated by ribosomes into proteins.
The DNA never unwinds completely, but rather does so region by region, because if it does so it would become so long that it wouldn't fit in the nucleus or cell.
A.
This is because BaSO₄ has the lowest solubility product out of all the substances.
