4 - The Periodic Table Flashcards
How many elements were discovered by 1869?
63
How is the modern periodic table arranged?
- Elements are arranged in order of increasing atomic number in periods
- Elements with similar properties are placed in the same vertical columns called groups
How did Mendeleev arrange the periodic table?
- He arranged elements in order of increasing relative atomic masses (sometimes he would do atomic weights instead)
- He left gaps in his table & did not always keep to this order
Why did Mendeleev not always keep to his order in the periodic table?
He sometimes swapped the positions of elements if he thought that better suited their chemical properties
How did Mendeleev use his table to predict the existence and properties of some elements not then discovered?
- Mendeleev assumed elements would continue to be discovered, so he left gaps for them
—> Helped him to position the existing elements - He used the gaps in his table to make predictions (based on the properties of nearby elements)
When Mendeleev arranged the periodic table in increasing atomic mass why was this sometimes not correct?
The relative abundance of isotopes of some pairs of elements in the periodic table
—> Means that some isotopes of a certain element is more abundant than others, meaning the RAM will be different
Give an example of a pair reversal in Mendeleev’s periodic table?
Iodine & Tellurium
- Iodine - 127
- Tellurium isotopes are tellurium-128 & tellurium-128
—> Relatively high abundance of tellurium isotopes gives it the higher RAM
What does Inert mean?
Does not react
How are elements arranged in the modern periodic table?
- Periods - In order of increasing atomic number
- Groups - Where elements have similar properties
Where are non-metals found in the periodic table?
How many electrons can the first shell contain up to?
2
How many electrons can the second & third shell contain up to?
8
What is an electronic configuration?
The way in which an atom’s electrons are arranged
How can you work out the electronic configuration of an element?
From its atomic number
What does the number of circles in a dot & cross diagram represent?
The period number that element is situated in
What does the number of electrons in the outermost shell in a dot & cross diagram represent?
The group number that element is situated in
What does the number of electrons in the all shells of an element represent?
Elements atomic number
