Answer:
1.) When Mendeleev arranged the elements in order of increasing atomic mass, the properties where repeated. Because the properties repeated themselves regularly, or periodically
2.) i can't really answer this one because it's not a direct question but if you get your periodic table and look at the list that it gave you look at which elements are in the same row and you you will get the correct answer that way
3.) and this question is referring back to question two so just pick one of the idem ( this means chose a name of an element) alkali elements and say because you mixed up alkaline and alkali and you figured it out by remembering what group and what row it was in
4.) name an element that can't be put into one group and chose this from the alkali group
5.) the number of valence electrons stays the same as you go up or down a group, but they increase as you go from left to right across the periodic table.
6.) sorry i don't really know how to explain this one
Explanation: