How many moles are in 2.8x10^24 atoms of silicon?

4.65 moles of Si.

Explanation:

Let x moles of silicon contains 2.8x10^24 atoms. 6.02x10^23 atoms are present in 1 mole of Si. Therefore 2.80x10^24 atoms are present in = 2.8x10^24/6.02x10^23 = 4.65 moles of Si

Okay so, each element always is abbreviated with a capital letter and a lowercase letter, so each each new elements starts with a capital letter. To answer these problem you have to find the element or compound and whats in the element/compound and count how many you have. Then, it transfers over the arrow to how many of each element you have.

I hope this helps! :)