How many grams are in 6.78 x 10^24 atoms of He?

45.05g

Explanation:

Based on the Avogadro's hypothesis, we understood that 1 mole of any substance contains 6.02x10^23 atoms.

From the above findings,

1 mole of He also contains 6.02x10^23 atoms.

1 mole of He = 4g

If 4g of He contains 6.02x10^23 atoms,

then Xg of He will contain 6.78x10^24 atoms i.e

Xg of He = (4x6.78x10^24)/6.02x10^23

Xg of He = 45.05g

Therefore, 45.05g of He contains 6.78x10^24 atoms

i had this on my unit activity, i can you if you are a plato student. are you a plato student?

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms