Scientists in Russia have just created a new element, adding to the ever-growing periodic table. This lesson will take you back in time, exploring the periodic table from it’s conception to its current day form.

You will investigate the following:

• How is organising the elements into the periodic table helpful?

• How are electrons arranged into energy levels?

• What links atomic structure and the periodic table together?

• Where do fireworks get their colours from?

So get your energy levels ready for some electron excitation!

This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to www.cosmosforschools.com

Chemistry

Periodic Table: Heralding its latest member

Introduction: Periodic table (P1)

The periodic table at the back of your textbook may be outdated – scientists in Russia have created a new element.

The position of an element on the periodic table is determined by how many protons it has in its nucleus. With 117, the newelement – dubbed ununseptium but also known simply as element 117 – is the heaviest confirmed so far, sitting at the far end of theperiodic table.

Element 117 was made by fusing together nuclei of two atoms containing 20 and 97 protons respectively. This process is not unlikethrowing two snowballs together and hoping they’ll stick to form a larger snowball – it’s not easy. And the larger atoms get, themore likely they are to decay because their numerous protons push each other out of the nucleus.

Atoms of the same element always have the same number of protons, but they can possess different numbers of neutrons. Thesedifferent forms are called isotopes. Scientists think that the varying ratio of neutrons to protons makes some isotopes more stablethan others.

Unfortunately, element 117 fell apart milliseconds after it was formed. Still, scientists hope that its creation will teach them howatoms stick together – and what makes them fall apart.

Read or listen to the full Cosmos magazine article here.

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Question 1

Describe: The term periodic means "shows a repeating pattern". One example of something periodic is the seasons – summer isalways followed by autumn, winter and spring, then back to summer. List three other things that are periodic.

Gather: Periodic table (P1)

Credit: Boing Boing Video / YouTube.

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Every naturally occurring atom in the universe was created either in the Big Bang, 14 billion years ago, or in a star. The Big Bangproduced the lightest elements: hydrogen and helium, and some lithium and beryllium. The rest of the helium, lithium andberyllium, and all of the other elements (with one or two exceptions not found in nature) up to number 92, uranium, were formedin stars.

Stars begin as mostly hydrogen. The immense force of the star's gravity fuses hydrogen into helium, releasing vast amounts ofenergy. When the hydrogen runs out the star starts to die. The other, heavier, elements are now formed up until, as a supernova,the star explodes sending the material out into space, where some of it forms planets.

Atoms consist of a central nucleus of protons and neutrons, with minute electrons flying around. Elements are substances made upof atoms with the same number of protons, also known as the element's atomic number. Compounds are substances where atomsof different elements are chemically bound to one another.

All the elements from number 93, neptunium, have been created artificially. They are all radioactive, meaning that when they areleft alone the atoms split into lighter elements. There are claims that element numbers 113, 115 and 118 have been created, butthese are still waiting for official confirmation, like that recently given for element 117.

The elements

Question 1

State: Uncharged atoms have the same number of electrons as protons. How many electrons are there in an uncharged atom ofelement 117?

The element carbon has an atomic number of 6 since it has 6 protons. Its most common isotope has a mass number of 12 since ithas 6 neutrons in addition to the 6 protons. The atomic number and mass number are often indicated on periodic tables. Examinethe example of carbon below before answering Question 2.

Did you know?

The mass number of an atom is a count of the total number of protons and neutrons in its nucleus, whereas its relative atomic

mass is the mean mass of all of the naturally occurring isotopes of the element taking into account their relative abundances.

Left: Periodic tables often include the atomic number and mass number of each element. Right: Graphite and diamondsare two different forms of carbon. Credit: Universal History Archive / UIG / Getty Images and Fabrice Coffrini / AFP / Getty

Images

Question 2

Find: Determine the atomic number, number of protons, number of electrons, mass number and number of neutrons for each ofthe following elements:

Element Atomic number Number of protons Number ofelectrons

Mass number Number ofneutrons

6 6 6 12 6

Amazingly, when 19th-century Russian chemistry professor Dmitri Mendeleev created the version of the periodic table that we usetoday, the atom itself hadn't even been discovered. He knew nothing about protons or atomic numbers.

Mendeleev compared all the elements to hydrogen, sorted them by their relative weights and organised them into family groupswith similar properties. His understanding of these family groups was so strong that he was able to leave gaps for, as yet,undiscovered elements and make predictions about their properties. Mendeleev lived long enough to see other scientists discoverthree elements for which he had left gaps – scandium, gallium and germanium. His predictions about the properties of theseelements turned out to be perfectly accurate.

Periodic table

Credit: TED-Ed / YouTube.

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Question 3

Recall: The first element to be discovered was

hydrogen.

aluminium.

helium.

phosphorus.

Question 4

Identify: Why were some elements easier to discover than others?

The periodic table is a method of arranging the elements, using atomic number as the main organising property. The horizontalrows are known as periods, whereas the vertical columns are known as groups. The organisation of the table allows us to observe arepeating pattern of properties for the groups.

Specific names have been given to the chemical family groupings of elements to describe some of theirproperties. Examine this periodic table before answering the following two questions.

Question 5

Label: Add the following terms to the periodic table below:

metals; metalloids; non-metals

Question 6

Label: Add the following terms to the periodic table below:

alkali metals; alkaline earth metals; transition metals; post transition metals; other non-metals; halogens; noble

gases; lanthanoids; actinoids

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Question 7

Locate: The Introduction section describes the discovery of a new element, number 117, temporarily known as ununseptium (Uus).Which group does element 117 belong to?

Question 8

Describe: Ununseptium, (Uus) was produced by colliding the atoms calcium-48 ( Ca) and berkelium-249 ( Bk) together. Write thereaction as a chemical equation.

Hint: Use the "Text" tool to write your equation. You will need to use the "Superscript" button to add the mass numbers and the "Add math"

button to add the equation arrow.

48 249

Process: Periodic table (P1)

Credit: iStock

The electron configuration (sometimes known as electronic structure) of an atom refers to the arrangement of its electrons inenergy levels surrounding the nucleus. Electron configuration is the structural feature of atoms that determines the chemicalproperties of an element.

More specifically, it is the number of valence electrons (electrons located in the highest energy level of an atom) that determines:

the group on the periodic table in which the element is located

whether the atom is metallic, non-metallic or metalloid

its chemical properties and therefore how it will chemically interact with other atoms

the combining ratio between atoms (i.e. whether it bonds with another atom in a 1:1 or 1:2 or 2:3 ratio etc.)

The remainder of this lesson focuses on the how the electron configuration of an atom determines its position in the periodic table.

Electron configuration

Credit: Joanne Beech / YouTube.

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Note: The method of arranging electrons described in the video clip works for elements 1-18. For elements with atomic numbers greater

than 18 a more complex method of writing electron configurations is needed, which you will learn about in senior Chemistry classes.

To summarise the video, you can deduce which period and group an element belongs to from its electron configuration, and viceversa. For example, the elements sodium (2,8,1) and chlorine (2,8,7) are both in the third period because their electronicconfigurations have three numbers. However, sodium is in group 1 and chlorine is in group 17. This information is represented inthe table below.

Number of protons Element name Number of electrons Simple electronconfiguration

Period Group

11 Sodium 11 2, 8, 1 3 1

17 Chlorine 17 2, 8, 7 3 17

Question 1

Organise: Add electrons (as green circles) to the following energy level diagrams and name each element.

Hint: When adding electrons, start with the innermost energy level.

a) b)

Question 2

Summarise: Complete the following table for elements in Question 1 above.

Number of protons Number of electrons Simple electron configuration Period Group

a)

b)

Question 3

Deduce: Using your understanding of electron configuration and how it determines an element's position in the periodictable, deduce the electron configurations for the elements with blue outlines. You may use a periodic table to assist you, but it isnot necessary.

One element has been completed for you. The element in period 3, group 1 is element number 11 (sodium). This element will have11 electrons organised into three energy levels, with only 1 valence electron. The electrons are arranged in a 2, 8, 1 configuration.

Question 4

Analyse: Given the following simple electron configurations, use a periodic table to determine the symbols and names of theelements represented.

Electron configuration Element symbol Element name

2,1

2,7

2,8,4

Question 5

Select: The University of Nottingham, UK has produced short video clips about each of the known elements, including elementnumber 117.

Access the periodicvideos.com website and select an element that you are not familiar with. Name your chosen element and, afterhaving watched the video clip, report three of the element's properties that you did not previously know.

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Apply: Periodic table (P2)

Experiment: Investigating flame colours of metal salts

Credit: Sully Science / YouTube.

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You have learned that each of the more than 110 elements has distinct properties and a characteristic atomic structure composedof protons, neutrons and electrons. You have also learned that the electrons in an atom occupy different, and very specific, energylevels, which can be represented using electron configurations.

When all of the electrons in an atom are at their lowest possible energy level, and positioned closest to the nucleus, they are said tobe in their ground state configuration.

However, the valence electrons in a metal atom are held so loosely by the atom’s positively charged nucleus that they can beexcited by the heat in a Bunsen burner flame. This causes them to travel away from the nucleus and move up to higher energylevels, increasing their potential energy. When an electron is in a higher energy shell than its ground state configuration, it is said tobe in an excited state.

At a higher energy level an excited electron is very unstable and so will naturally return to its ground state configuration, so as to bestable again. As the electron returns to its original energy level it releases light energy.

Background

For most group 1 and 2 metal elements the wavelength of theemitted light, produced when an excited electron returns to itsground state, is within the visible part of theelectromagnetic spectrum. This means that we can see it as oneof the colours of the rainbow.

The exact colour (wavelength) of light produced in this way ischaracteristic for each element, which makes the flame test auseful qualitative method in chemistry for determining theidentity or possible identity of the metal element in acompound. Colours differ because each type of element hasdifferent spacings between its energy levels.

The colours produced by metal atoms are utilised by fireworkmanufacturers. By including different metal salts, or mixtures ofmetal salts, in the exploding shells of their fireworks, theseartists can produce beautiful displays in nearly all the colours ofthe rainbow.

Credit: iStock

To investigate the flame colours produced by a range of metal salt compounds and then use your results to determine which metalsalt is present in a common household chemical.

Test tube racks for small test tubes

Bench mats

Bunsen burners

Small test tubes, labelled with names of metal salts and hazard warnings

Wooden splints, pre-soaked in distilled water and then placed into relevant metal salt solutions

Small test tubes, labelled with distilled water

Approximately 0.5 M solutions of some or all of the following:

Aim

Materials

Potassium chloride (Low hazard)

Lithium chloride (Harmful)

Sodium chloride (Low hazard)

Rubidium chloride (Low hazard)

Caesium chloride (Low hazard)

Calcium chloride (Irritant)

Strontium chloride (Irritant)

Copper(II) chloride (Harmful, Danger to the environment)

Common household chemical - cream of tartar

1. Tie back long hair and put on safety glasses and lab coats.

2. Note how many different flame test ‘stations’ are set up around the classroom.

3. Prepare a qualitative data table for your results – you will be recording the name of each metal salt solution and yourobservations during the flame tests.

4. Perform your first flame test by placing the wooden splint (soaked in the metal salt solution) into the coolest part of theBunsen burner flame then slowly moving it into the hottest part of the flame for 2 seconds. Be sure not to burn the woodensplint.

5. Immediately after viewing the flame colour, cool the wooden splint by placing it into the test tube of water.

6. Replace the cooled wooden splint into its original salt solution.

7. Record the name of the metal salt solution tested and your observations. Try to be as descriptive as possible with yourobservations – for example, a metal salt solution that produces a red flame may be more accurately described as ‘brick red’ or‘fire engine red’.

8. Perform the remaining flame tests around the classroom, recording your results as you go along.

9. One of the ‘stations’ will be set up with a solution of the common household chemical, cream of tartar; perform the flame testfor this solution in exactly the same way as the others.

10. Clean up following your teacher’s instructions.

Wear a lab coat and safety glasses at all times.

If you have long hair make sure to tie it back.

Be cautious around the Bunsen burner.

Some of the chemicals being tested are hazardous – you should follow the teacher’s instructions about safe handling of thesechemicals.

Independent variable – type of metal salt solution

Dependent variable – colour produced when metal salt solution is placed into Bunsen burner flame

Note: The independent variable is what is being changed each time, the dependent variable is what you are measuring or testing

It is possible that atoms of different metal elements produce different colours when placed into the Bunsen burner flame becauseeach element has a unique number of protons and therefore a unique electron configuration.

Procedure

Safety Information

Variables

Hypothesis

Question 1

Collect: Use the project space below to present your results. You should construct a table of results but you may also includephotos, video or other representations.

Results

Discussion

Question 2

Justify: Explain why a different wooden splint was used for eachmetal salt solution

Question 3

Assess: Identify the metal element present in the commonhousehold chemical, cream of tartar, using your results tosupport your answer.

Question 4

Apply: Using a periodic table, state the group and period numbers of the metal element you identified in the common householdchemical, cream of tartar and, in your own words, explain what these numbers mean.

Question 5

Evaluate: Identify some limitations to the experimental designthat prevent you from collecting more reliable and accuratedata.

Question 6

Evaluate: Suggest changes that you could make if you were torepeat this experiment, which address the limitations youidentified.

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Question 7

Conclude: Write a concluding statement that addresses the aim of the experiment and the hypothesis.

Conclusion

Career: Periodic table (P2)

Julia Abbott always keeps a periodic table with her in her wallet. “You never know when you might need to know the relativeatomic mass of element 72,” she jokes. (“It’s Hafnium, 178.49!”)

Julia’s love for the periodic table doesn’t come as a surprise –she has a PhD in organometallic synthesis, the study ofcompounds containing carbon atoms and metals. But aftergraduation Julia decided that she didn’t want to work in a lab –she was more interested in helping others learn about science.So after earning her degree, she became a project manager forscience education programs at Oak Ridge AssociatedUniversities in Tennessee, USA.

As a project manager, Julia’s job is to coordinate events for theScience Saturday program for primary and secondary schoolstudents. She organises the teams of scientists and teacherswho create presentations and activities for the events. She alsoworks with them to make sure that the science material coveredis fun and easy to understand. Each event within the programfocuses on a different topic, and Julia has worked on everythingfrom x-rays to rainbows to robots.

Sometimes Julia organises educator programs for teachers, too.She loves seeing them get just as excited about science as theirstudents, especially since some of her own teachers had helpedher discover her love for science. Without their encouragement,Julia says, she wouldn’t have pursued science as a career. Growing up, Julia thought that, as a girl, she would be no goodat maths or chemistry. But by Year 12 she was the only girl inher honours Physics class and was scoring top marks!

When she isn't getting crafty with her hands-on science lessons,Julia enjoys other hands-on activities like quilting, cross-stitch,and embroidery, as well as biking and cooking.

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Question 1

Interview: Arrange a short chat with one of your current or past science teachers and find out:

what they most enjoy about teaching science;

whether teaching was their first career;

what strategies they use to try and make their lessons fun and easy to understand; and

what advice they would give to a year 10 student about finding the right career path to follow.

Cosmos Live Learning team

Lesson authors: Hayley Bridgwood and Kathryn GraingerProfile author: Megan Toomey

Editors: Bill Condie, Jim Rountree and James WhitmoreArt director: Robyn Adderly

Education director: Daniel Pikler