Hi there!

We can use the following conversions to solve:
Total mass --> amount of mols --> amount of atoms (Avogadro's number)
Begin by calculating the amount of boron trifluoride in 3.61 grams:
3.61 g * (1 mol BF₃ / 67.8 g) ≈ 0.0532 mol BF₃
Use avogadro's number to convert:
0.0532 mol * 6.02× 10²³atoms / 1 mol = 3.203 × 10²² atoms
The answer is the mass number! (:
Covalent bond is the term that is being used to describe the bonds in the compounds that are created due to the sharing of one or more electrons. One of the best example of the simplest covalent bond is the bond that is being created when two isolated hydrogen atoms come together to form an H2 molecule. An isolated hydrogen atom has one proton and electron being combined by the force of attraction from the opposite-charged articles. When a pair of isolated hydrogen atom combines, two forces of attraction are created coming from each of the isolated hydrogen atom.
Answer:
You need to dilute 8 M HCl to 0.35 M to make 457 mL.
Explanation:
Use the equation M₁V₁=M₂V₂
Convert the mL to L : 20 mL= 0.02 L
8 M x 0.02 L = 0.35 M x V₂
V₂ = 0.4571429 L = 457 mL