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Flashcards in C4b Deck (7):
1

What are isotopes?

-different forms of the same element, which have the same number of protons, but a different number of neutrons
-same atomic number but different mass numbers
-different atomic number means different element altogether

2

What are the rows on the periodic table called and what do they tell us?

-periods
-each new period represents another full shell of electrons
-the period an element belongs to corresponds with the number of shells of electrons it has

3

What are the columns on the periodic table called and what do they tell us?

-groups
-the group an element belongs to corresponds to the number of electrons in its outer shell
-group 8's outer shells are full

4

What did Dobereiner do?

-1828
-put elements into groups of three (triads) based on chemical properties
-middle element in a triad had a relative atomic mass that was the average of the other two

5

What did Newlands do?

-1864
-noticed that every eighth element had similar properties and so listed some known elements in rows of seven
-these sets of eight were called Newlands' Octaves
-the pattern broke on the third row
-he left no gaps so is work was criticised because:
*his groups contained elements that didn't have similar properties
*he mixed up non-metals and metals
*no gaps left for undiscovered elements

6

What did Dmitri Mendeleev do?

-1869
-around around 50 known elements in a Table of Elements with gaps
-put elements in order of atomic number like Newlands
-he found he had to leave gaps in order to keep elements with similar properties in the same vertical groups
-gaps predicted properties of the undiscovered elements
-when they were found they fitted the pattern

7

Why did Mendeleev's table make more sense discoveries on atomic structure were made?

-each element has an atomic number one more than the previous element
-the pattern of the periodic table matched the way electrons are arranged in atoms