C2.1 - R* Development of the periodic table Flashcards
Chemists were finding what almost every year during the 19th century?
Chemists were finding new elements almost every year during the 19th century
Chemists were finding new elements almost every year during the 19th century.
What were chemists trying very hard to do during the 19th century?
Chemists were trying very hard to find patterns in the behaviour of the elements during the 19th century
What would finding patterns in the behaviour of elements allow chemists in the 19th century to do?
Finding patterns in the behaviour of elements would allow chemists in the 19th century to:
- Organise the elements
- Understand more about chemistry
What did John Dalton do?
John Dalton arranged the elements in order of their atomic weights
What did John Dalton do, in 1808?
In 1808, John Dalton published a table of elements in his book:
‘A New System of Chemical Philosophy’
What did John Newlands do, in 1864?
In 1864, John Newlands:
- Built on Dalton’s ideas
- Also arranged the known elements in order of mass
What did John Newlands do, after noticing that the properties of every 8th element seemed similar?
After noticing that the properties of every 8th element seemed similar, John Newlands produced a table showing his ‘law of octaves’
After noticing that the properties of every 8th element seemed similar, John Newlands produced a table showing his ‘law of octaves.’
What did John Newlands not do?
John Newlands did not take into account that chemists were still discovering new elements
Where did John Newlands’ table only really work for?
John Newlands’ table only really worked for the known elements up to calcium
What was other scientists’ reaction to John Newlands’ ideas?
Other scientists:
- Ridiculed John Newlands’ ideas
- Refused to accept them
In 1869, how many elements had been identified?
In 1869, around 50 elements had been identified
In 1869, around 50 elements had been identified.
What did the Russian chemist Dmitri Mendeleev do with all the 50 known elements?
The Russian chemist Dmitri Mendeleev arranged all of the 50 known elements into his Table of Elements
Why were there not many doubts left that Mendeleev’s table was a breakthrough in scientific understanding?
They were not many doubts left that Mendeleev’s table was a breakthrough in scientific understanding, because a few years later, new elements were discovered with properties that closely matched Mendeleev’s predictions
When Mendeleev was working, the noble gases had not been discovered, but when he met the same problem with other elements of ordering by atomic weights resulting in certain elements (such as argon) being placed in groups with different chemical properties, he did what?
When Mendeleev was working, the noble gases had not been discovered, but when he met the same problem with other elements of ordering by atomic weights resulting in certain elements (such as argon) being placed in groups with different chemical properties, he simply changed their order where necessary to keep elements with similar properties in the same group
When was it that scientists began to find out more about the structure of the atom?
Scientists began to find out more about the structure of the atom at the start of the 20th century
At the start of the 20th century, only until scientists began to find out more about the structure of the atom, the issue of what could be solved?
At the start of the 20th century, only until scientists began to find out more about the structure of the atom, the issue of certain elements breaking the periodic pattern could be solved
The issue of certain elements breaking the periodic pattern was solved, because what?
The issue of certain elements breaking the periodic pattern was solved, because the:
- Elements in the periodic table are in order of their number of protons (atomic number)
- Existence of isotopes accounted for the oddly heavy atomic weights of some elements
Why were some elements placed in the wrong group, in early periodic tables?
In early periodic tables, some elements were placed in the wrong group, because:
- Elements were placed in the order of relative atomic mass
- Did not take into account their properties
Why did Mendeleev leave gaps in his Table of Elements?
Mendeleev left gaps in his Table of Elements to ensure that elements with similar properties stayed in the same groups
Mendeleev left gaps in his Table of Elements to ensure that elements with similar properties stayed in the same groups.
What did some of these gaps indicate?
Some of these gaps indicated the existence of undiscovered elements
Not all elements fit in with Mendeleev’s pattern.
Example
For example, argon
Mendeleev left gaps in his Table of Elements to ensure that elements with similar properties stayed in the same groups.
Some of these gaps indicated the existence of undiscovered elements and allowed Mendeleev to predict what their properties might be.
What happened when they were found?
When they found, they fitted the pattern
Mendeleev left gaps in his Table of Elements to ensure that elements with similar properties stayed in the same groups.
Some of these gaps indicated the existence of undiscovered elements and allowed Mendeleev to predict what their properties might be.
When they found, they fitted the pattern and it helped confirm Mendeleev’s ideas.
Example
For example, Mendeleev made really good predictions about the:
1. Chemical
2. Physical
properties of an element he called ekasilicon
What did the discovery of isotopes in the early 20th century confirm?
The discovery of isotopes in the early 20th century confirmed that Mendeleev was correct to not place elements in a strict order of atomic mass, but to also take account of their properties
John Dalton arranged the elements in order of their atomic weights, which had been measured in what?
John Dalton arranged the elements in order of their atomic weights, which had been measured in various chemical reactions
In 1864, John Newlands built on Dalton’s ideas and also arranged the known elements in order of mass, but noticed what?
In 1864, John Newlands:
1. Built on Dalton’s ideas
2. Also arranged the known elements in order of mass
,but noticed that the properties of every 8th element seemed similar
After noticing that the properties of every 8th element seemed similar, John Newlands produced a table showing his ‘law of octaves.’
John Newlands did not take into account that chemists were still discovering new elements.
He assumed what?
John Newlands assumed that all the elements had been found
After noticing that the properties of every 8th element seemed similar, John Newlands produced a table showing his ‘law of octaves.’
John Newlands did not take into account that chemists were still discovering new elements.
John Newlands assumed that all the elements had been found, so he did what?
John Newlands assumed that all the elements had been found, so he filled in his octaves
After noticing that the properties of every 8th element seemed similar, John Newlands produced a table showing his ‘law of octaves.’
John Newlands did not take into account that chemists were still discovering new elements.
John Newlands assumed that all the elements had been found, so he filled in his octaves, even though what?
John Newlands assumed that all the elements had been found, so he filled in his octaves, even though some of his elements were not similar at all
John Newlands’ table only really worked for the known elements up to calcium, before what?
John Newlands’ table only really worked for the known elements up to calcium, before the pattern broke down
In 1869, around 50 elements had been identified.
The Russian chemist Dmitri Mendeleev arranged all of the 50 known elements into his Table of Elements, in order of what?
The Russian chemist Dmitri Mendeleev arranged all of the 50 known elements into his Table of Elements, in order of their atomic weights
In 1869, around 50 elements had been identified.
The Russian chemist Dmitri Mendeleev arranged all of the 50 known elements into his Table of Elements, in order of their atomic weights.
Then he did what?
Then Mendeleev arranged them so that a periodic (regularly occurring) pattern in their properties could be seen
In 1869, around 50 elements had been identified.
The Russian chemist Dmitri Mendeleev arranged all of the 50 known elements into his Table of Elements, in order of their atomic weights.
Then Mendeleev arranged them so that a periodic (regularly occurring) pattern in their properties could be seen.
He left what?
Mendeleev left gaps for elements that had not yet been discovered
In 1869, around 50 elements had been identified.
The Russian chemist Dmitri Mendeleev arranged all of the 50 known elements into his Table of Elements, in order of their atomic weights.
Then Mendeleev arranged them so that a periodic (regularly occurring) pattern in their properties could be seen.
Mendeleev left gaps for elements that had not yet been discovered.
Then he used his table to do what?
Then Mendeleev used his table to predict what their properties should be
When Mendeleev was working, the noble gases had not been discovered, but when he met the same problem with other elements of ordering by atomic weights resulting in certain elements (such as argon) being placed in groups with different chemical properties, he simply changed their order where necessary to keep elements with similar properties in the same group.
This problem was what for decades?
This problem was a mystery for decades
Mendeleev left gaps in his Table of Elements to ensure that elements with similar properties stayed in the same groups.
Some of these gaps indicated the existence of undiscovered elements and allowed Mendeleev to do what?
Some of these gaps:
- Indicated the existence of undiscovered elements
- Allowed Mendeleev to predict what their properties might be
Not all elements fit in with Mendeleev’s pattern.
For example, argon.
Argon atoms have what than potassium atoms?
Argon atoms have a greater average relative mass than potassium atoms
Not all elements fit in with Mendeleev’s pattern.
For example, argon.
Argon atoms have a greater average relative mass than potassium atoms.
Ordering by atomic weights would result in argon (a noble gas) being what?
Ordering by atomic weights would result in argon (a noble gas) being in the same group as reactive metals such as:
- Sodium
- Lithium
Not all elements fit in with Mendeleev’s pattern.
For example, argon.
Argon atoms have a greater average relative mass than potassium atoms.
Ordering by atomic weights would result in argon (a noble gas) being in the same group as reactive metals such as sodium and lithium.
It would also group potassium (an extremely reactive metal) with what?
It would also group potassium (an extremely reactive metal) with the unreactive noble gases
Not all elements fit in with Mendeleev’s pattern.
For example, argon.
Argon atoms have a greater average relative mass than potassium atoms.
Ordering by atomic weights would result in argon (a noble gas) being in the same group as reactive metals such as sodium and lithium.
It would also group potassium (an extremely reactive metal) with the unreactive noble gases.
So argon’s position in the periodic table must be what to maintain the periodic pattern?
So argon’s position in the periodic table must be before potassium to maintain the periodic pattern
Not all elements fit in with Mendeleev’s pattern.
For example, argon.
Argon atoms have a greater average relative mass than potassium atoms.
Ordering by atomic weights would result in argon (a noble gas) being in the same group as reactive metals such as sodium and lithium.
It would also group potassium (an extremely reactive metal) with the unreactive noble gases.
So argon’s position in the periodic table must be before potassium to maintain the periodic pattern, even though what?
So argon’s position in the periodic table must be before potassium to maintain the periodic pattern, even though the average mass of its atoms is heavier than that of potassium’s atoms
Mendeleev left gaps in his Table of Elements to ensure that elements with similar properties stayed in the same groups.
Some of these gaps indicated the existence of undiscovered elements and allowed Mendeleev to predict what their properties might be.
When they found, they fitted the pattern and this helped to do what?
When they found, they fitted the pattern and this helped to confirm Mendeleev’s ideas
Mendeleev left gaps in his Table of Elements to ensure that elements with similar properties stayed in the same groups.
Some of these gaps indicated the existence of undiscovered elements and allowed Mendeleev to predict what their properties might be.
When they found, they fitted the pattern and it helped confirm Mendeleev’s ideas.
For example, Mendeleev made really good predictions about the chemical and physical properties of an element he called ekasilicon, which we know today as what?
For example, Mendeleev made really good predictions about the:
1. Chemical
2. Physical
properties of an element he called ekasilicon, which we know today as germanium
The discovery of isotopes in the early 20th century confirmed that Mendeleev was correct to not place elements in a strict order of atomic mass, but to also take account of their properties.
Why do isotopes of the same element occupy the same position on the periodic table?
Isotopes of the same element occupy the same position on the periodic table, because they have different atomic masses, but the same chemical properties
