What is the little number after an element in a chemical equation called

Which phrase best describes the rock's texture? 1.jagged grains 2.coarse grains 3.rounded grains 4.non-banded grains

What neutral atom is isoelectronic to mn+4

Calculate the expected ph values of the buffer systems from the experiments (a,b,c,d), using the henderson- hasselbalch equation, ph-pka+log[a-]/[ha]. use for pka values carbonic acid= 6.37, and acetic acid= 4.75.