The “Zen” of tea-cups

1. The “Zen” of tea-cups

2. Long long ago, a scholar wanted to learn about Zen from a learned master

3. The learned master sat him down, and started pouring him a cup of tea……

4. But he poured and poured until the tea overflowed….. And he still continued pouring……

5. Master! The cup is already full! Stop pouring tea into the tea cup!

6. You are like this tea cup…… You come forth with you your own knowledge and thinking.

7. If you do not empty your tea cup, how do you expect me to teach you about Zen? ….

8. When someone brings with them their own thinking and knowledge, sometimes they do not hear the message that other people is trying to convey to them……

9. When 2 people engage in a conversation, often they are anxious to convey their own thinking……

10. But the result is that they can only hear an echo of what they have said, and nothing else.

11. In this topic, many of you will bring with you a lot of your prior knowledge. Sometimes, many of these (whether you believe it or not) ARE misconceptions.

12. I need you to compare / contrast what you know with what I am presenting to you, and clarify any doubts – especially those you think that I have made a mistake.

13. But in case you forget them, you might want to jot it down on a piece of paper… and remember to ask them soon after the lecture.

14. Atoms, Molecules, and Stoichiometry Introduction, Elementary particles, and Relative masses

15. Some notes about this topic • The assessment objectives are given on the first page of your notes • Make sure you are able to achieve all of them at the end of the topic – monitor your own learning. • The lecture notes is designed with a column for your “notes”. • It was found that students who write their own notes / comments relate to their notes better • “Notes” on the right margin are also part of your notes.

16. What will I learn? • What is an atom? • What are the particles that make up an atom? • How do I represent an atom in writing? • How do I calculate the number of neutrons and the charge of an atom? • What is a molecule and formula unit? • What is relative mass?

17. 2 Introduction • Stoichiometry is the study of • the quantitative composition of chemical substances • the quantitative changes that take place during chemical reactions

18. Atoms • An atom is the smallest indivisible particle of an element • The “paper clip” analogy 

19. Particle Symbol Relative mass Relative charge Atoms • An atom is the smallest indivisible particle of an element • An atom is made up of 3 sub-atomic particles proton p 1 +1 neutron n 1 0 electron e- -1

20. Atoms • The number of protons in an atom is calledatomic number (Z) • The total number of protons and neutrons in an atom is called mass / nucleon number (A) • An atom can be represented as follows: Chemical symbol Mass number Atomic number

21. Atoms • The number of protons in an atom is calledatomic number (Z) • The total number of protons and neutrons in an atom is called mass / nucleon number (A) • An atom can be represented as follows:

22. 3 Atoms • Atoms of the same element have the same number of protons • Same atomic number • But can have different number of neutrons • Can have different mass number • Atoms of the same element having different number of neutrons are called isotopes

23. Atoms • Atoms of the same element have the same number of protons • Same atomic number • But can have different number of neutrons • Can have different mass number • Atoms of the same element having different mass numbers are called isotopes

24. Atoms • Atoms of the same element having different mass numbers are called isotopes

25. Atoms • Neutral atoms have equal number of protons and electrons • Hence, isotopes have the same number of electrons  same chemical properties • A particle have unequal number of protons and electrons is called an ion.

26. Particle Number of protons Number of neutrons Number of electrons Atoms 17 18 17 17 20 17 19 21 19 19 20 19

27. Atoms Particle Number of protons Number of neutrons Number of electrons 92 146 92 8 8 10 11 12 10

28. Molecules and Formula Units • A molecule is a group of atoms covalently bonded together in an element or a compound • The smallest particle of simple covalent compounds that can exist alone under ordinary conditions • E.g. N2, CO2, NH3 are covalent molecules

29. Structure of ice (H2O)

30. Molecules and Formula Units • A molecule is a group of atoms covalently bonded together in an element or a compound • The smallest particle of simple covalent compounds that can exist alone under ordinary conditions • E.g. N2, CO2, NH3 are covalent molecules • For an ionic compound, • we define a formula unit as the smallest group of atoms which the formula of the compound can be established • E.g. NaCl, Ca(NO3)2, and Al2O3

31. Cl- Na+ Ionic Compound • Example: NaCl

32. 4 Relative Mass • The masses of atoms are very small (10-23g) •  chemists use a relative atomic mass scale • Used to compare the mass of different atoms • Relative atomic mass scale: • Reference selected: 12C • On this scale, the mass of a 12C atom is assigned a value of 12.0 • The relative mass of other atoms are obtained by comparing with the mass of 12C atom

33. mass of one particle • Relative mass of a particle • = x mass of one 12C atom Relative Mass • To calculate relative mass:

34. mass of one isotope • Relative mass of a particle • = x mass of one 12C atom Relative Isotopic Mass • The relative isotopic mass • Mass of an isotope compared to the mass of a 12C atom • To calculate relative isotopic mass:

35. average mass of one atom • Relative mass of a particle • = x mass of one 12C atom Relative Atomic Mass • Most elements consist of a mixture of isotopes •  relative atomic mass must be representative of the mass and relative amount of each isotope • The relative Atomic mass • Average mass of an atom compared to the mass of a 12C atom • To calculate relative atomic mass:

36. Total mass of mangos • Average mass of a mango • = Total number of mangos Relative “Mango” mass • Imagine inside your fridge you’ve got Mangos from 3 different countries: • What is the average mass of the mangos?

37. Relative “Mango” mass • Imagine inside your fridge you’ve got Mangos from 3 different countries: • What is the average mass of the mangos? (3 x 12) + (2 x 10) + (5 x 15) • Average mass of a mango • = 3 + 2 + 5

38. Relative “Mango” mass • Imagine inside your fridge you’ve got Mangos from 3 different countries: • What is the average mass of the mangos? • Average mass of a mango 13.1 g • =

39. (Relative abundance x relative isotopic mass) • Relative mass of a particle • = (relative abundance) ?!?!?! Relative Atomic Mass • An alternative equation: Sum up all the values contained in the set

40. Relative Atomic Mass • Example 1:Calculate the relative atomic mass of rhenium given that rhenium consist of two isotopes 185Re and 187Re in the ratio 2 : 3 = 186.2 (No units)

41. Meaning: the average mass of one rhenium atom is 186.2 times heavier than the mass of a 12C atom Relative Atomic Mass • Example 1:Calculate the relative atomic mass of rhenium given that rhenium consist of two isotopes 185Re and 187Re in the ratio 2 : 3 = 186.2

42. Relative Atomic Mass • Example 2:The abundance of the isotopes of chlorine are:Calculate the relative atomic mass of chlorine = 35.46

43. What have I learnt? • What is an atom? • What are the particles that make up an atom? • How do I represent an atom in writing? • How do I calculate the number of neutrons and the charge of an atom? • What is a molecule and formula unit? • What is relative mass?

44. End of Lecture 1 Have a great weekend (Do review your notes)