C2- the periodic table Flashcards
What did Dalton arrange the elements in order of?
Atomic weights.
What did John Newlands do?
Also arranged the known elements in order of mass + noticed properties of every 8th element seemed similar.Produced table showing his ‘law of octaves’.
What was John Newlands’ error?
He did not realise chemists still discovering new 1s.
He assumed all elements had been found.
Filled his octaves even though some elements not similar at all.
His table only worked for known elements up to Calcium before pattern broke down.
What did Mendeleev do?
Arranged 50 elements in a table. Placed them so periodic (regularly occurring) pattern in properties seen.
Left gaps for elements not discovered yet. Then used his table to predict what their properties should be.
What could cause doubts about Mendeleev’s periodic table?
Not all elements fit in Mendeleev’s pattern- argon is example: ordering by atomic weights result in argon being in same group as reactive metals. Mendeleev changed order wherever necessary to keep elements with similar properties in same group.
Mendeleev was working before noble gases discovered.
When did scientists start solving issue of certain elements breaking periodic pattern?
20th century.
What are elements in the periodic table ordered in?
Number of protons (atomic number).
What did the existence of isotopes account for?
Oddly heavy atomic weights of some elements.
What are the transition metals?
The block containing elements most people probably think of when word ‘metal’ mentioned, like iron, copper, silver + gold.
These metals not usually very reactive some like silver + gold very unreactive.
What are the noble gases?
Non-metal elements that are very unreactive difficult to combine these with other elements as have stable electronic structures.
What are the non-metals?
Elements with low boiling points, many liquids or gases at room temperature and pressure.
What are the reactive metals?
Metals react vigorously with other elements (oxygen or chlorine), + with water. All soft- some can cut with with knife.
What are the alkali metals?
Group contains; lithium, sodium, potassium, rubidium, cesium, francium.
1st 3 as rubidium + cesium are too reactive for use in schools. Francium extremely unstable radioactive element.
What are the group 1 + 7 trends?
Group 1= lithium-> sodium-> potassium-> rubidium-> cesium. (->more reactive).
Group 7= fluorine
What are the physical properties of transition elements?
Good conductors of electricity and heat.
Hard and strong.
High densities.
High melting points (exception: mercury-liquid at room temperature).
