Hi!
You would not want to use a stopper when<span> combining two unknown substances because the gasses made from the combination could end up creating to much pressure and explode.</span>
The isotopes are elements with the same number of protons but different number of neutrons.
Boron atomic number is 5. That is the number of protons.
The natural occurring isotopes of boron contain 5 or 6 neutrons. Other, non stable isotopes, contain from 1 to 16 neutrons.
1 it a 2 it b 3 it c 4 it be 7 it a
Happy Holidays! :)

Looking at the information given in the description, the experiment is testing for the effects of the different salts on the growth of the plants.
This means that the type of salt is the independent variable, or the variable being manipulated and tested.
To ensure fair results, some parts of the experiment would need to be kept the same, which is the control. The only answer choice that makes sense in this instance is A. water.
<span>Get a periodic table of elements. ...Find your element on the periodic table. ...Locate the element's atomic number. ...Determine the number of electrons. ...Look for the atomic mass of the element. ...<span>Subtract the atomic number from the atomic mass.</span></span>