Nice! Well done! 2 atoms of C weigh $$2 \times 12 = 24 \, \mathrm{amu}$$. This is exactly the mass of an Mg atom.
We had said that atoms were like letters in a language. Like different letters made up words, which made up sentences and books, different atoms made up everything else.

But, most letters do not occur in a sentence on their own. They combine with other letters to form words.
Which letter here is also a word?
• A
• T
• W
• L