What is the oxidation state of each element in the species mn(clo4)3? i'm going over oxi-redox reactions from a long time ago and i'm trying to remember properly. mn=3+ cl=7+ and oxygen=2- right?

The following are the answers:
 =oxygen  equals to a charge of 2-
number of atoms is -24
=Mn equals to the charge of +3
Mn=  3+3x-24=0
let x be the charge of Cl, so:
23-3=3x
20/3=x
=6.67 or 7
x= 7
= Cl has a charge of +7

You are right about your answers

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant. 

Neither model is able to show the reactivity of potassium.