4.what did j. j. thomson observe when he applied electric voltage to a cathode ray tube in his famous experiment?
a. the stream of cathode ray particles was moving very slowly.
b. the glass opposite of the negative electrode started to glow.
c. the electric voltage had little effect on the stream of particles.
d. the tube contained two pieces of metal that served as electrodes.
11.the table below gives the data that is needed to calculate the average atomic mass of element b.
b-10(isotope), 10.01(atomic mass), 19.91(relative abundance %)
b-11(isotope), 11.01(atomic mass), 80.09(relative abundance %)

Correct option is B

B.The glass opposite of the negative electrode started to glow.

In his experiment, tubes were two electric plates, producing a positive anode and a negative cathode, which he expected that it would deflect the rays. As he supposed, the rays were deflected by the electric charge, proving beyond doubt that the rays were made up of charged particles bearing a negative charge.

Boron is a chemical element in the periodic table with symbol B and has atomic number 5.

Boron has two naturally occurring isotopes Boron-10 and Boron-11. The average atomic mass of these are calculated as

(10.01×0.198) + (11.01×0.802) =  10.81 amu

So, the average atomic mass of the Boron isotopes is 10.81 amu.

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.

it's all four options.