Which of these id an indication that a chemical reaction has occurred? a) formation of a gas b) boiling of a substance c) melting of a substanced) freezing of a substancd

Which type of orbits are found in the principal energy level n = 2 a - s b - s, f c - s, d d - s, p e - s, p, d

Tin has ten stable isotopes. the heaviest, 124sn, makes up 5.80% of naturally occuring tin atoms. how many atoms of 124sn are present in 82.0 g of naturally occurring tin? what is the total mass of the 124sn atoms in this sample?

What volume would 2.25 moles of ne has occupy at stp?