elements of life

1. elements of life

2. STORYLINE EL 1 By the end of this STORYLINE, you should be able to … • explain how different elements form by nuclear fusion reactions • describe the differences between emission and absorption spectra • explain what an emission spectrum tells us • Explain what is meant by radioactive decay • How radioactive materials are used

3. EL 1 Where do the chemical elements come from? The Big Bang • Most scientists believe that a long time ago, the Universe we live in was incredibly small, dense and hot. • Many different observations support this view and it now appears that the Universeunderwent a very dramatic event right at the beginning, known as the Big Bang. • Estimates put the Big Bang some 13 to 17 thousand million (13 - 17 billion) years ago. • Since then the Universe has expanded, cooled down and has become much less dense.

4. EL 1 MAKING NOTES FROM AN ARTICLE • Note taking is a crucial skill in higher education. • Your task is to make notes on pg 3 of the EL storyline.

5. EL 1 C.I.2.1 C.I.2.2 • What is a nuclear reaction? • In what way does it differ to a chemical equation? • What is the atomic number of an element? • How can we find out what it is? • What is the mass number of an element? • How can we find out what it is?

6. EL 1 • Stars form when the hydrogen in gas clouds join together by nuclear fusion and turns into helium, releasing vast quantities of light and heat energy. • In their centres, intense heat and pressure cause further nuclear reactions to occur and heavier elements are formed. • A hot wind is then generated which drives away some of this dust and gas. Planets condense out of these and surround the star in a solar system

7. EL 1 The Sun – a lightweight among stars • What is meant by a ‘heavyweight star’? • What is a supernova? • What element causes the Supernova to occur? • Is the Sun a heavyweight star? • What will happen once it’s supply of Hydrogen is exhausted? • Explain the terms ‘white dwarf’ and ‘red giant’ Ass 1 Act EL 1.2

8. C.I.2.3 C.I.6.1 • Spectroscopy gives us many clues about the Universe; that is, what it contains. • It relies on the fact that matter is made from particles and these particles interact with radiation from the electromagnetic spectrum … EL 1 How do we know so much about outer space?

9. Electromagnetic spectrum A spectrograph allows us to analyse this radiation as it is characteristic of particular elements

10. EL 1 • What is the difference between an emission and an absorption spectrum? • What do they both have in common? • What does each line on a spectrum represent? • From which part of the Sun can we detect the radiation on a spectrograph on Earth? • What is meant by the terms: ground state; excited state?

11. Ass 2 EL 1.3 flame tests • Read notes on pg 8 ‘Our Solar System’ • Summarise the information in 3 sentences. Swap your work with a neighbour, asking them to correct/improve it until you both agree on the most important facts EL 1 Our Solar System C.I.2.2 half lives EL 1.4 radioactive decay and half life

12. STORYLINE EL 2 By the end of this STORYLINE, you should be able to … • Understand how the various elements in the universe combined to make various compounds, particularly the molecules that make up living things

13. EL 2 the molecules of life • Hydrogen is the most common element in space. • It exists as atoms rather than as H2 molecules. Why is this? • Where do molecules, rather than atoms, form in space? C.I.3.1 types of chemical bonding EL 2.1

14. EL 2 Cold Chemistry and the ‘Molecules of Life’ • Where are molecules likely to form in space? • Study table 1 • What is significant about these species? C.I.3.2 Shapes of Molecules EL 2.2 EL 2.4 CHECK YOUR NOTES

15. STORYLINE EL 3 By the end of this STORYLINE, you should be able to … • Describe the categories to which various elements in the body belong and the function they have in the body • Explain the origins of the Periodic Table and how it is organised

16. EL 3 What are we made of? • Chemists describe the human body to be made of ‘a mixture of compounds and elements’ • Describe each of the terms in bold print • Elements are further classified into 3 main groups • Name and define each of these groups

17. The trace element, Calcium … • A lack of calcium in the body can lead to a condition called osteoporosis • To find out how much of the dietary calcium is taken up by the bloodstream, a tracer technique is used Ass 3 • An alternative to using potentially dangerous radioactive isotopes is to use an element with similar characteristics to calcium – i.e. in the same group of the Periodic Table

18. When bones are formed, strontium, in Group 2 like calcium, is taken up by the bones, in a similar way to calcium • Strontium emits a specific, characteristic frequency of red light, when a flame test is performed. • The amount of Strontium found to be present in the bones is proportional to the amount of calcium. This can tell the analyst how well the bones are taking up calcium.

19. EL 3 Counting number of Atoms • Refer to Table 2 • Why is studying mass an inaccurate way of determining the quantities of elements in a compound? • What is the best way to determine the amount of an element in the body? • The chemist uses a system called THE MOLE to enable them to determine the exact number of atoms of a particular element in a compound, even though they are too small to count.

20. EL 3 Making and Analysing Epsom Salts C.I.1.1 Amount of Substance Ass 4 (optional)

21. STORYLINE EL 4 By the end of this STORYLINE, you should be able to … • understand how Mendeleev developed the Periodic Table by leaving gaps and rearranging some elements from their atomic mass order and how subsequent research validated this knowledge • given relevant information, discuss other examples of how scientific research can be used to assess the validity of a discovery

22. EL4 Looking for Patterns in the Elements • As more and more elements were being discovered, chemists began to try and make sense of how they behaved by arranging them into patterns • For example, some were arranged into ‘families’ by organising their behaviour. We now refer to these as groups • By 1850, 59 elements out of the 92 naturally occurring elements were known, which prompted even more searching for relationships and patterns in the elements

23. EL4 Looking for Patterns in the Elements • Contributors to the work were: • Johann Dobereiner • Lothar Meyer • John Newlands • Dmitri Mendeleev

24. EL4 Looking for Patterns in the Elements • Mendeleev’s organisation of the Periodic Table was seen to be the most logical and make the most sense • He arranged the elements in order of their atomic masses • However when doing so, he put elements that were similar to each other in the same vertical column, paying particular attention to chemical properties.

25. Examples of how this worked well: swapping the elements tellurium and iodine as he reasoned that iodine behaved more like chlorine and bromine Leaving ‘a gap’ between silicon and tin, where later upon it’s discovery, germanium would occupy the space, making the prediction that an element belonged there that had yet to be discovered. He called this element ‘eka-silicon’ EL4 Looking for Patterns in the Elements

26. However, Mendeleev used values for atomic masses that were not accurate. He and others at the time had no way of knowing about the existence of isotopes (a much later discovery) We have this information at our disposal today, thanks to a technique called mass spectrometry EL4 Looking for Patterns in the Elements C.I.6.5 Mass Spectrometry EL 4.2 Using data from a mass spectrometer