Answer:
Discovery and Naming: The first evidence of helium was obtained on August 18th, 1868 by French astronomer Jules Janssen. While in Guntur, India, Janssen observed a solar eclipse through a prism, whereupon he noticed a bright yellow spectral line (at 587.49 nanometers) emanating from the chromosphere of the Sun.
Yeah what is the question
Since the equation for density is d=m/v, you can multiply both sides by m in order to get m by itself {d(v)=m}. Plug the volume and density in (1.1x7.9) and you will get 8.69. If you are using proper sig figs, then it will be 8.7g.
One of the differences I can think of is that hydrogen is no longer listed as a group I element.
According to the mendeleev tables that I looked up, hydrogen is catorgrized as a group I element, along with Lithium, sodium, Potassium etc. However, nowadays, hydrogen does not belong to any groups in the periodic table. This is because there are arguments about whether hydrogen belongs to group I. Group I elements are all alkali metals, while hydrogen is not. However, some people says that hydrogen only have one outer shell electron so it should be in group I. Some people even say hydrogen should belong to group VII because it only needs one more electron in order to achieve the duplet of electrons.
Therefore as you may notice, hydrogen in modern periodic tables are put in the center of the periodic table on the top.
Answer:
good electrical conductor
lustre in appearance