In the previous blog post of the Periodic Table Mini Series, we have discussed about the properties of a special group of elements in the Periodic Table – known as Metalloids.
Today, we will look into the Group I elements, also known as the Alkali Metals.
All the Group I elements have the following common properties:
- Soft & Silvery solids
- Low densities and low melting points
- React vigorously with cold water to form an alkaline solution of the metal hydroxide? and hydrogen gas
- Burn brightly when heated in chlorine gas to give a white solid metal chloride product
- Atoms of Group I elements have 1 electron in their outer shells
- Atoms of elements tend to form cation with a charge of +1 in compounds
If you are asked in Chemistry Exams / in Chemistry Tuition Class / by your Chemistry Teacher / by your Chemistry Tutor – on predicting properties of other Group I elements, remember this 2 points:
- Based on Known Properties of Lithium, Sodium and Potassium
- The changes down the group
and this brings us into looking at the trends of Group I elements,
Generally, as We Go Down The Group:
- Melting points of elements decrease
- Elements become more reactive
Let us check out a GCE O Level Examination Question:
Francium (atomic number 87) is in Group I of the Periodic Table.
(i) Suggest the physical appearance of Francium
(ii) How would you expect the melting point of francium to compare with that of sodium?
(iii) Suggest with an equation, what would be observed if a piece of francium is put into cold water? Explain what happens to the pH of the solution produced.
Let us check out some common errors made by many students in O Level Chemistry Examinations, before i provide you with the correct answers (suggested) – this has proved to be effective in learning the correct Chemistry Concepts by students, based on feedbacks from those that have purchased Up Your Chemistry Grades Now!
Students’ Common Answers:
(i) It is a silvery hard solid since it is a metal.
(ii) It is lower than sodium.
(iii)It would reactive to produce an alkaline solution and hydrogen gas.
2Fr? +? 2H2O? –> 2FrOH? +? H2
The pH of the solution would be alkaline.
Let us see how the student(s) fare..
Examiners / Markers’ Comments:
(i) Wrong answer by student. Group 1 metals is indeed silvery solid, but it is soft, NOT hard! Many students did not realise that Group 1 metals are soft. NOT ALL metals are hard. Group 1 is the exception.
(ii) Answer is not complete to gain the full marks. You must give a reason to support your prediction. Better answer would be: “Francium has a lower melting point than sodium, since it is lower then sodium in Group 1.
(iii)The chemical equation is correct. But the student will loose marks in his/her answers. He/She did not mention that Francium will EXPLODE with added to cold water, since Group 1 metals get more reactive down the group. He/She also did not mention that the pH would be around 12-13, which is like sodium hydroxide – a strong alkali.
Hope you find the above discussion to be helpful towards your learning of Chemistry in a more effective & efficient manner.
Until the next post…
[…] Part I Periodic Table Mini Series – Part II Periodic Table Mini Series – Part III Periodic Table Mini Series – Part IV Periodic Table Mini Series – Part V Periodic Table Mini Series – Additional Video Tips […]