The Periodic Table

Question 1

What so the odeon periodic table?

Answer 1

It’s a chart that arranges these elements in a way that’s useful to chemists

Question 2

Thanks to the periodic table what can chemists do?

Answer 2

Can make sense of patterns and trends which lets them predict the properties of elements

Question 3

In early 1869 What was the problem Russian chemist Dmitri Mendeleev (1834-1907) faced and how did he solve it?

Answer 3

He was busy writing the second volume of his chemistry textbook and could not decide which elements it made sense to write about next. His solution was to construct a table that led to the periodic table we know today

Question 4

How many elements had chemists discovered by 1869?

Answer 4

63 and Mendeleev arranged these elements in order of increasing relative atomic masses (called atomic weights then)

Question 5

Unlike other chemists who had tried to arrange elements in order of relative atomic mass what did Mendeleev do in his table

Answer 5

He left gaps

Question 6

What did Mendeleev sometimes do to the elements if he thought that better suited their chemical properties and those of their compounds?

Answer 6

Swapped some elements around

Question 7

Turn to page 26

Answer 7

And look at paragraph 3

Question 8

What did Mendeleev assume?

Answer 8

That elements would continue to be discovered so he left gaps for them

Question 9

How did Mendeleev leaving gaps help him to position the existing elements?

Answer 9

So that vertical columns contained elements with increasing relative atomic mass, and horizontal rows contained elements with similar chemical properties

Question 10

Mendeleev continued to work on his periodic table. By 1871 what had he settled on?

Answer 10

A table in which elements with similar properties were arranged into vertical columns, just as today

Question 11

Turn to page 27

Answer 11

And look at Mendeleev’s periodic table

Question 12

What did Mendeleev use the gaps in his table for?

Answer 12

To make predictions about the properties of u discovered elements, based on the properties a out the properties of nearby elements. One set of predictions was for an element in 1875, it’s properties closely fitted those Mendeleev had predicted for eka-aluminium

Question 13

Turn to page 27

Answer 13

And look at the table

Question 14

How many known elements are there?

Answer 14

Over 100

Question 15

Development of the periodic table continued after Mendeleev’s first tables and what was discovered near the end of the 20th century?

Answer 15

An entire group of inert or very unreactive elements

Question 16

Even though the chemists had not predicted the existence of the group of unreactive elements what group in the periodic table did they easily fit into but what was the problem?

Answer 16

Group 0, however pair reversals were not properly explained and there were still gaps. This began to change in 1913 due to a physicist called Henry Mosley

Question 17

When scientists were. Beginning to accept the periodic table what was a elements atomic number?

Answer 17

It was just its position in the table

Question 18

Instead of an elements atomic number just its position in the table what did mostly show?

Answer 18

It is a physical property of an elements atoms

Question 19

What did Moseley fire at different elements and what did he discover?

Answer 19

High-fired electrons which made them give off X-rays and he discovered that for every step increase in atomic number there was a step change in the energy of these X-rays

Question 20

What did Moseley realise an atomic number was equal to?

Answer 20

To the number of positive charges in the nucleus of an atom, and the particle that carries this charge was discovered a few years later. So the atomic number must be the. Number of protons in a nucleus

Question 21

The element in the modern periodic table are arranged in order of increasing atomic number,z, when this is done:

Answer 21

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 other elements are metals)
The iodine-tellurium pair reversal is explained

Question 22

Turn to page 29 and look at the second paragraph

Answer 22

And the table

Question 23

What did more X-ray analysis show?

Answer 23

That just seven elements between hydrogen (z=1) and uranium (z=92) were left to be discovered. These were all discovered between 1917 and 1945. Neptunium, the first element with an atomic number above 92 was discovered in 1940. Other such ‘transuranium’ elements continue to be discovered and can be placed all over the periodic table

Question 24

What is electrons filling shells in an atom like?

Answer 24

Rather like filling a bus one seat at a time from the front

Question 25

In an atom electrons occupy electron shells arranged around the nucleus. The shells can be modelled in diagrams as circles with the electrons drawn as dots or crosses on each circle. What is the way in which an atoms electrons are arranged called?

Answer 25

Electron configuration

Question 26

Each shell can contain a different number of electrons. How many do the first 20 contain (hydrogen to calcium)?

Answer 26

The first she’ll can contain up to two electrons

The Avondale and third shells can contain up to eight electrons

Question 27

How do shells containing electrons become full?

Answer 27

Electrons occupy the shells, starting with the innermost she’ll and working outwards as each one becomes full

Question 28

Electron configuration can also be written out rather than drawn. For an example what’s the sodium electron configuration?

Answer 28

2.8.1 (2 on the first shell, 8 on the second and 1 on the third)- the numbers show how many electrons occupy a shell and the full stops separate each shell

Question 29

Turn to page 30 and 31 and look

Answer 29

At the configuration for chlorine and connections with the periodic table and the did you know box

Question 30

How did Mendeleev arrange elements into the periodic table?

Answer 30

He arranged the elements into the order of increasing atomic mass

Question 31

How did Mendeleev predict the existence and properties of some elements yet to be discovered?

Answer 31

He left gaps in his table to make predictions about the properties of undiscovered elements, based on the properties of nearby elements.

Question 32

How was Mendeleev ps early ideas later supported by evidence?

Answer 32

One set of predictions was for an element he called eka-aluminium. When gallium was discovered shortly afterwards in 1875 its properties closely fitted those Mendeleev had predicted for ska-aluminium

Question 33

What is the atomic number?

Answer 33

It is the number of protons in the nucleus

Question 34

How are the elements arranged in the modern periodic table?

Answer 34

They are arranged in order of increasing atomic number

Question 35

What are the positions of the metals and non-metals?

Answer 35

Non-metals are on the right of the table (the other elements are metals)

Question 36

What does electron configuration mean?

Answer 36

It’s the ways in which an atoms electrons are arranged

Question 37

Explain the links between an elements position in the periodic table and its electronic configuration

Answer 37

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 other elements are metals)
The iodine-tellurium pair reversal is explained