The number of protons in the nucleus of the atom, I believe. c:
Explanation:tr
a) Molar mass of HF = 20 g/mol
Atomic mass of hydrogen = 1 g/mol
Atomic mass of fluorine = 19 g/mol
Percentage of an element in a compound:

Percentage of fluorine:

Percentage of hydrogen:

b) Mass of hydrogen in 50 grams of HF sample.
Moles of HF = 
1 mole of HF has 1 mole of hydrogen atom.
Then 2.5 moles of HF will have:
of hydrogen atom.
Mass of 2.5 moles of hydrogen atom:
1 g/mol × 2.5 mol = 2.5 g
2.5 grams of hydrogen would be present in a 50 g sample of this compound.
c) As we solved in part (a) that HF molecules has 5% of hydrogen by mass.
Then mass of hydrogen in 50 grams of HF compound we will have :
5% of 50 grams of HF = 
Answer: Pseudopodia are temporary and cytoplasm-filled parts of the cell membrane that are able to change their form in order to move. They are used in some eukaryotic cells to move around or to eat. Most cells that do this are called amoeboids.
Answer:
Explanation:
SF4 forms a trigonal bipyramidal shape and its molecular shape is that of a "see-saw".
Since sulfur is in 3rd period, it violates the octet rule and has more than 8 electrons accompanying its valence shell.
Here's a picture of lewis structure and electron geometry.
I think the answer is C. 02