History of the Periodic Table

Match the following descriptions to the person they describe: Mendeleev or Moseley.


Mendeleev arranged elements according to atomic mass
Mendeleev predicted properties for elements missing from his periodic table
Moseley English physicist, used x-ray diffraction
Mendeleev had some elements out of place
Moseley arranged elements according to atomic number
Moseley discovered that each element has a unique atomic number
Mendeleev Russian chemist, created first valid periodic table of the elements
Moseley placed all elements in the right place according to properties

What property is identical to the elements in each column of the periodic table?

Click to reveal the answer

Electron distribution – each element’s last term has the same number of electrons located in the same type of sublevel.
For example:
Li = 2s¹

Na = 3s¹

K = 4s¹

Write the noble gas configuration for each of the following elements. Highlight the table to reveal the answers.

Lithium [He]2s1
Magnesium [Ne]3s2
Copper Copper doesn’t follow the rules as expected. [Ar]4s13d10
Bromine [Ar]4s23d104p5
Silver Silver does not follow the rules as expected. [Kr]5s14d10 is the actual configuration. One 5s electron moves to the higher 4d sublevel because it is more stable there.
Tellurium [Kr]5s24d105p4

(Hint: don’t forget the f-block!)

[Rn]7s25f4 Remember that the principal quantam number is 2 fewer than the period number for electrons in f sublevels.