The atoms ,molecules, or compound present at the start of a chemical reaction that parcitipate in the reaction . which part of a chemical reaction does this define?

The atoms ,molecules, or compound present at the start of a chemical reaction that parcitipate in the reaction are the reactants.

Explanation:

The chemical reaction is the way in which one substance reacts against another. So, a chemical reaction consists of the transformation of some substances into others, that is, the process of arranging atoms and bonds when chemical substances come into contact.

In a chemical reaction, the initial substances are called reactants, while the new substances obtained are called products.

So, the atoms ,molecules, or compound present at the start of a chemical reaction that parcitipate in the reaction are the reactants.

they should be similar or the same

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west