C4- The Periodic Table Flashcards
How did Mendeleev arrange the periodic table / what was it like
In order of increasing relative atomic mass
He sometimes swapped elements due to them being better suited to chemical properties
He assumed that elements would continue to be discovered so he left gaps for them
Vertical columns contained elements with increasing relative atomic mass
Horizontal rows contained elements with similar chemical properties
How did Mendeleev make predictions
Used gaps in the table to make predictions about the properties of undiscovered elements based of properties of nearby elements
Eg. Predicted eka-aluminium but discovered as gallium
What did Moseley find out
Discovered that for every step increase in atomic number there was a step change in the energy of X Ray’s when he fired high energy electrons at different elements
How are elements arranged in modern periodic table
Elements in a row or period are in order of increasing atomic number
Elements with similar properties are in the same column or GROUP
Non metals are on the right of the table
The iodine-tellurium pair reversal is explained
Explain the iodine-tellurium pair reversal
Iodine exists naturally as I^127 but tellurium has several different isotopes about 20% of its atoms are Te^126 but nearly 60% are Te^128 or Te^130 so jts relative atomic mass is greater than that of iodine
What’s the symbol for atomic number
Z
How are electrons represented on an atom
They are dots or crosses on each circle that represents a shell
The way atoms are arranged is called the electronic configuration
Tell me the rules of the shells
The first shells can contain up to 2 electrons
The 2 and 3 shells can contain up to 8 electrons
Start with the innermost shell working out until it’s full
How can electronic configuration be written
Write it with numbers eg. 2.8.1 is sodium - full stops seperate each shell
What’s the number of occupied shells equal to according to the first 20 elements in table hydrogen to calcium
The period number (horizontal rows)
Also the number of electrons in outer shell
Is equal to its group
