<span>The hardest known mineral is diamond.
</span>
Answer:
The Earth is shaped by many geological processes. ... Processes caused by forces from within the Earth are endogenous processes. Exo is a prefix meaning "out", and endo is a prefix meaning "in". Many exogenous (extraterrestrial) forces are caused by other bodies in the Solar System.
That statement is true
it was easy to organize 'all' the elements in a group of threes because back then they only knew about 15 - 20 elements
hope this helps
The test for this is fairly simple.
We take a glowing match or splint near the gas sample, if the glow intensifies, oxygen is present.
If a lit splint or match goes out with a popping sound, this means that hydrogen is present.
