Why didn't mendeleev include helium , neon and argon in his periodic table?

Answer choices are:

A. These elements did not fit in with his pattern.

B. These elements are gases and he didn't include gases.

C. The atoms of these elements had no atomic mass.

D. These elements had not yet been discovered.

Correct answer choice is:

D. These elements had not yet been discovered.

Explanation:

Mendeleev would have no precise logic to presume there were lacking elements when they can be distributed by various units. But he did note bearings and was capable to divine some holes based on these bearings. The whole column of noble gases, though, could be dropped as it was a periodic recess, not a recess in the period.

Mendeleev added the noble gases later, near the edge of his life, during enough proof was received.

what is the volume occupied by 40 grams of argon gas (ar) at standard conditions? what volume, in liters, is occupied by 1.5 x 1023 

in chemistry, adhesion and cohesion are attractive forces that exist between molecules. they hold the molecules together from each other. they are different in that adhesive force exists between molecules of different substance while cohesive force happens between molecules of same substance.

adhesion between water and glass causes water molecules at the edge of water and glass interface to climb up the wall in a narrow glass tube. this is called capillary action. cohesion is what gives glass its shape and causes water to form a droplet.