Per Wolfram Alpha, sulfur is 4.62 times heavier; the earth is 0.002% lithium, so it would experience a net gain of 3.62 * mass of earth * 0.00002, or 4.3e20kg. That’s 7.24e-5 times heavier, so not much in the grand scheme of things.
Note that I’m neither a chemist, a physicist, or an astronomer, so I make no guarantee that I did this right.
What is the total mass gain if all lithium(3) became sulfur(16)? How many planets would become stars overnight?
Per Wolfram Alpha, sulfur is 4.62 times heavier; the earth is 0.002% lithium, so it would experience a net gain of 3.62 * mass of earth * 0.00002, or 4.3e20kg. That’s 7.24e-5 times heavier, so not much in the grand scheme of things.
Note that I’m neither a chemist, a physicist, or an astronomer, so I make no guarantee that I did this right.
Edit: misplaced decimal
4 zeros not 3. 0.00002
Probably none of them
Related, there’s a Kurzgesagt video on what happens if you turn the entire earth into gold: https://www.youtube.com/watch?v=VB_GWz25B3Q
You have to make assumptions on what you keep constant: mass? volume? density? Each scenario is amusing in its own apocalyptic way.