What was the significant change that Glenn Seaborg made to Mendeleev’s periodic table?

The Seaborg introduced the whole new row to the periodic table called actinides.

Explanation:

The american scientist Glenn Seaborg has many important contribution the chemistry. His work made a significant change in the mendeleev's periodic table. He introduced new row that is placed below the lanthanides row, called actinides.

He was co-discoverer or principle discoverer of plutonium and einsteinium. He was responsible for the discovery of more than 100 medical isotopes.

Thus, the Seaborg introduced the whole new row to the periodic table called actinides.

not really sure but thinking 1.54 mm/us

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.