C3 - The Periodic Table Flashcards
Who was the first person to invent a periodic table?
Newlands
In the early 1800s, what were the only 2 ways to categories elements and why weren’t anymore known?
Their chemical and physical properties
Their relative atomic mass
Atomic number wasn’t discovered because there was no knowledge of atomic structure (protons and electrons)
Describe Newlands’ periodic table
Newlands had invented a law of octaves which said that every eighth element (in order of atomic mass) had similar properties
He listed all of the currently known elements in rows of 7 so that his law of octaves was followed
What were the 3 ways that Newlands’ work was criticized?
His groups contained elements that didn’t have similar properties like carbon and titanium (titanium is a transition metal)
He mixed up metals and non-metals
He didn’t leave any gaps for undiscovered elements
Who invented the next periodic table?
Mendeleev
Describe Mendeleev’s periodic table
He put the elements in order of atomic mass like Newlands but he left gaps in order to keep elements with similar properties in the same vertical columns
He left big gaps above the transition metals (first 2 rows) to follow his rule
When new elements were discovered and put in the table according to their mass number, they fitted in terms of properties
Why didn’t many scientists think the periodic table was important?
There wasn’t much evidence to say that the elements really did for together in that way
What were the 3 reasons that people started supporting the periodic table?
Newly discovered elements fitted into the gaps he left
It was a useful tool for predicting properties of elements
Atomic structure was discovered and this matched up with his periodic table
What are the 2 ways that the modern periodic table is different to Mendeleev’s?
It is ordered by atomic number instead of mass number
Each period has one more shell of electrons
Describe how the modern periodic table is organised
The group number represents the number of electrons in the outer shell and the period number represents the number of shells of electrons
The mass number of an element is the number of protons and neutrons and the atomic number is the number of protons
The middle block is the transition metals which don’t belong to a group
The staircase-shaped line divides the metals on the left from the non-metals
