The periodic table Flashcards
1
Q
who discovered the periodic table
A
150 years ago by dimitiri mendeleev
2
Q
groups
A
verticle columns, number of valence electrons
3
Q
periods
A
horizontal rows, number of shells
4
Q
what is the exception to the group rule
A
helium, it is located in group 18 but only has 2 valence electrons, it is here because it is unreactive like the other elements of group 18
5
Q
what do elements with the same amount of valence electrons share
A
similar chamical prperties
