C2.1 - R* Development of the periodic table

Question 1

Chemists were finding what almost every year during the 19th century?

Answer 1

Chemists were finding new elements almost every year during the 19th century

Question 2

Chemists were finding new elements almost every year during the 19th century.
What were chemists trying very hard to do during the 19th century?

Answer 2

Chemists were trying very hard to find patterns in the behaviour of the elements during the 19th century

Question 3

What would finding patterns in the behaviour of elements allow chemists in the 19th century to do?

Answer 3

Finding patterns in the behaviour of elements would allow chemists in the 19th century to:

1. Organise the elements
2. Understand more about chemistry

Question 4

What did John Dalton do?

Answer 4

John Dalton arranged the elements in order of their atomic weights

Question 5

What did John Dalton do, in 1808?

Answer 5

In 1808, John Dalton published a table of elements in his book:
‘A New System of Chemical Philosophy’

Question 6

What did John Newlands do, in 1864?

Answer 6

In 1864, John Newlands:

1. Built on Dalton’s ideas
2. Also arranged the known elements in order of mass

Question 7

What did John Newlands do, after noticing that the properties of every 8th element seemed similar?

Answer 7

After noticing that the properties of every 8th element seemed similar, John Newlands produced a table showing his ‘law of octaves’

Question 8

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?

Answer 8

John Newlands did not take into account that chemists were still discovering new elements

Question 9

Where did John Newlands’ table only really work for?

Answer 9

John Newlands’ table only really worked for the known elements up to calcium

Question 10

What was other scientists’ reaction to John Newlands’ ideas?

Answer 10

Other scientists:

1. Ridiculed John Newlands’ ideas
2. Refused to accept them

Question 11

In 1869, how many elements had been identified?

Answer 11

In 1869, around 50 elements had been identified

Question 12

In 1869, around 50 elements had been identified.

What did the Russian chemist Dmitri Mendeleev do with all the 50 known elements?

Answer 12

The Russian chemist Dmitri Mendeleev arranged all of the 50 known elements into his Table of Elements

Question 13

Why were there not many doubts left that Mendeleev’s table was a breakthrough in scientific understanding?

Answer 13

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

Question 14

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?

Answer 14

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

Question 15

When was it that scientists began to find out more about the structure of the atom?

Answer 15

Scientists began to find out more about the structure of the atom at the start of the 20th century

Question 16

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?

Answer 16

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

Question 17

The issue of certain elements breaking the periodic pattern was solved, because what?

Answer 17

The issue of certain elements breaking the periodic pattern was solved, because the:

1. Elements in the periodic table are in order of their number of protons (atomic number)
2. Existence of isotopes accounted for the oddly heavy atomic weights of some elements

Question 18

Why were some elements placed in the wrong group, in early periodic tables?

Answer 18

In early periodic tables, some elements were placed in the wrong group, because:

1. Elements were placed in the order of relative atomic mass
2. Did not take into account their properties

Question 19

Why did Mendeleev leave gaps in his Table of Elements?

Answer 19

Mendeleev left gaps in his Table of Elements to ensure that elements with similar properties stayed in the same groups

Question 20

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?

Answer 20

Some of these gaps indicated the existence of undiscovered elements

Question 21

Not all elements fit in with Mendeleev’s pattern.

Example

Answer 21

For example, argon

Question 22

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?

Answer 22

When they found, they fitted the pattern

Question 23

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

Answer 23

For example, Mendeleev made really good predictions about the:
1. Chemical
2. Physical
properties of an element he called ekasilicon

Question 24

What did the discovery of isotopes in the early 20th century confirm?

Answer 24

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

Question 25

John Dalton arranged the elements in order of their atomic weights, which had been measured in what?

Answer 25

John Dalton arranged the elements in order of their atomic weights, which had been measured in various chemical reactions

Question 26

In 1864, John Newlands built on Dalton's ideas and also arranged the known elements in order of mass, but noticed what?

Answer 26

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

Question 27

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?

Answer 27

John Newlands assumed that all the elements had been found

Question 28

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?

Answer 28

John Newlands assumed that all the elements had been found, so he filled in his octaves

Question 29

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?

Answer 29

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

Question 30

John Newlands' table only really worked for the known elements up to calcium, before what?

Answer 30

John Newlands' table only really worked for the known elements up to calcium, before the pattern broke down

Question 31

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?

Answer 31

The Russian chemist Dmitri Mendeleev arranged all of the 50 known elements into his Table of Elements, in order of their atomic weights

Question 32

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?

Answer 32

Then Mendeleev arranged them so that a periodic (regularly occurring) pattern in their properties could be seen

Question 33

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?

Answer 33

Mendeleev left gaps for elements that had not yet been discovered

Question 34

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?

Answer 34

Then Mendeleev used his table to predict what their properties should be

Question 35

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?

Answer 35

This problem was a mystery for decades

Question 36

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?

Answer 36

Some of these gaps: 1. Indicated the existence of undiscovered elements 2. Allowed Mendeleev to predict what their properties might be

Question 37

Not all elements fit in with Mendeleev's pattern. For example, argon. Argon atoms have what than potassium atoms?

Answer 37

Argon atoms have a greater average relative mass than potassium atoms

Question 38

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?

Answer 38

Ordering by atomic weights would result in argon (a noble gas) being in the same group as reactive metals such as: 1. Sodium 2. Lithium

Question 39

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?

Answer 39

It would also group potassium (an extremely reactive metal) with the unreactive noble gases

Question 40

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?

Answer 40

So argon's position in the periodic table must be before potassium to maintain the periodic pattern

Question 41

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?

Answer 41

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

Question 42

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?

Answer 42

When they found, they fitted the pattern and this helped to confirm Mendeleev's ideas

Question 43

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?

Answer 43

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

Question 44

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?

Answer 44

Isotopes of the same element occupy the same position on the periodic table, because they have different atomic masses, but the same chemical properties