# Understand the Development of the Periodic Table

In this worksheet, students will learn about the structure of the Periodic Table and how it was developed.

### QUESTION 1 of 10

All materials - living and non-living - are made of atoms. They combine in millions of different ways to make everything we see around us, even us! Scientists discovered the structure of the atom and this helped them to arrange the elements in order on the periodic table. Mendeleev was the pioneer, arranging the elements in order of relative atomic mass. He realised that the properties of elements were related to their relative atomic mass and put the elements with similar properties into vertical groups, the same groups we see on the periodic table today. However, at the time, not all elements had been discovered, but that did not put him off. He simply realised that there were more elements to be discovered and left gaps on the periodic table for those elements! Mendeleev went even one step further to predict the properties of the missing elements and turned out to be right when those elements were finally discovered! A feat of brilliance that has earned him a spot in every scientist's ‘great scientist’ list.

Dmitri Mendeleev (1834-1907), a Russian chemist, published the periodic table in 1869.

But Mendeleev wasn’t the first person to try and do that and he had help from his predecessors. A guy called Döbereiner in the 1800’s put the elements into groups of threes called the triads. He noticed that they all had similar properties and that when you took an average of their atomic mass, it always turned out to be the same as the middle mass. Well, it happened most of the time…

Then a guy called Newlands came along and noticed that there were patterns with every eight elements when you lined them up by atomic mass. So lithium, sodium and potassium all had similar properties and were all eight spaces away from each other – this was a big deal. But it only worked for the first twenty elements, so something was going on.

Mendeleev worked out that if you put the two groups together and then left gaps, you could make it all work – he had just discovered the periodic table.

In 1913 a British chemist, Henry Moseley, realised that it would be better to use atomic number rather than mass, so he put the final touches to the periodic table, after resolving some issues that had surfaced from Mendeleev's work.

The periodic table, as we know it today, is shown below. Familiarise yourself with the position of alkali metals (Group 1), halogens (Group 7), metals and non-metals, transition metals and also noble gases (Group 0).

You will need to know this really well for your exam, so spend some time studying it very carefully before moving on to the questions.

Who was the pioneer of the periodic table?

Sir Isaac Newton

James Joules

Dmitri Mendeleev

Henry Moseley

In which group on the periodic table are the halogens?

Group 0

Group 7

Group 1

In which group on the periodic table are the noble gases?

Group 0

Group 13

Group 3

In which group on the periodic table are the alkali metals?

Group 0

Group 1

Group 13

Where are the transition metals mainly found on the periodic table?

Left

Right

Centre

Where can you find most metals on the periodic table?

On the left

On the right

In the centre

Where can you find most non-metals on the periodic table?

On the left

On the right

In the centre

What was special about Mendeleev​'s periodic table?

It contained all of the atoms

He left gaps for undiscovered elements

He put atoms with similar properties together

He put the atoms in order of atomic weight

Why do we now know that Mendeleev's periodic table is the best way of grouping the elements?

We can see the patterns in the electron structures

He arranged the elements in no particular way

It doesn't work for all of the elements

What did Moseley change in Mendeleev's periodic table that improved it?

He rearranged it in order of atomic mass

He rearranged it according to elements' properties

He rearranged the elements in order of atomic number and their properties

• Question 1

Who was the pioneer of the periodic table?

Dmitri Mendeleev
EDDIE SAYS
Dmitri Mendeleev created the first edition of the periodic table. He now has an element named after him (mendelevium).
• Question 2

In which group on the periodic table are the halogens?

Group 7
EDDIE SAYS
The halogens are Group 7.
• Question 3

In which group on the periodic table are the noble gases?

Group 0
EDDIE SAYS
The noble gases are in Group 0 - they are helium, neon, argon, krypton, xenon and radon. If you're not sure about some of these questions, go back and have another look at the periodic table.
• Question 4

In which group on the periodic table are the alkali metals?

Group 1
EDDIE SAYS
The alkali metals are Group 1. They are on the left-hand side of the periodic table and are the first group (hence being called Group 1).
• Question 5

Where are the transition metals mainly found on the periodic table?

Centre
EDDIE SAYS
Transition metals are mainly in the centre.
• Question 6

Where can you find most metals on the periodic table?

On the left
EDDIE SAYS
Still not sure? Check out that periodic table again to help you get this sorted. Most metals are on the left. As you move towards the right-hand side, you hit the semi-metals in a diagonal line, like carbon and silicone. Then you get the gases and non-metals like oxygen and argon.
• Question 7

Where can you find most non-metals on the periodic table?

On the right
EDDIE SAYS
Hopefully, your answer to the previous question will have helped you with this one! Most non-metals are on the right. They all form up in a neat diagonal line on the right-hand side of the periodic table.
• Question 8

What was special about Mendeleev​'s periodic table?

He left gaps for undiscovered elements
EDDIE SAYS
How did you get on with this one? Watch out for the exact wording of each option. Mendeleev realised that we were working with an incomplete list of the elements and so he left gaps in his table. He described 'eca-aluminium' 20 years before it was discovered and re-named galium. He was a true genius.
• Question 9

Why do we now know that Mendeleev's periodic table is the best way of grouping the elements?

We can see the patterns in the electron structures
EDDIE SAYS
Even after his death, we now know that he must have been correct, since when we look at the atoms, we see that there are patterns in the electron structures as well as in their properties.
• Question 10

What did Moseley change in Mendeleev's periodic table that improved it?

He rearranged the elements in order of atomic number and their properties
EDDIE SAYS
Mendeleev was the driving force behind the periodic table, but one change was made in later years that made it even better. In 1913 a British chemist, Henry Moseley, realised that it would be better to use atomic number rather than mass, so he put the final touches to the periodic table. How are you doing with learning the key elements of the periodic table? There's a lot to grasp but it really is important to know this for the exam. You've made a great start by completing this activity. Well done.
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