Hydrogen and oxygen react to form water. At an atomic level, how do we know that a chemical reaction has occurred? *
1 point
Hydrogen molecules are negative, and oxygen positive.
For every oxygen atom, two hydrogen atoms are needed.
The hydrogen and oxygen atoms regroup into a new molecule.
Oxygen atoms are much larger than hydrogen atoms.

Explanation:

The hydrogen and oxygen atoms regroup into a new molecule.

Look into intermolecular forces! :) it will show you different types of bonding/how molecules will bond

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

im pretty sure its b