I think the best answer is the last option. A scatter plot is the appropriate type of graph for the student to use to show the percent samples per group. This plot is somewhat similar to line graphs. However, they are use for a specific purpose which is to show the relationship between two parameters. In this case, the correlation between pH and the percent of samples.
We use the following formula to calculate the number of atoms:
n (mol) = N(number of atoms) / NA
N(He) = n(mol) · NA
N(He) = 2,0 moles · 6.02·1023 = 12.04·1023 atoms
If an atom gains an electron and gets a negative charge because of it, it is a negatively charge ion AKA an anion.

What is the difference between a quantity and a unit?
Answer:
Physical quantities are a characteristic or property of an object that can be measured or calculated from other measurements. Units are standards for expressing and comparing the measurement of physical quantities. All units can be expressed as combinations of four fundamental units.
Hope this helps!!!

Answer:
explanation and image attached
Explanation:
Our aim is to draw a structure of XeO2F2 whith the least formal charges. We must remember that the compound has 34 valence electrons.
To obtain the least formal charges then Xe must have a total of twelve electrons on its valence shell instead of eight.
The other atoms around the central Xe atom are arranged as shown in the image attached.
Image Credit: UCLA