the “zen” of tea-cups

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The “Zen” of tea-cups

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CLong long ago, a scholar wanted to learn about Zen from a learned master

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CThe learned master sat him down, and started pouring him a cup of tea……

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

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

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

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CIf you do not empty your tea cup, how do you expect me to teach you about Zen?

….

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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……

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

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

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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.

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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.

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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.

Atoms, Molecules, and Stoichiometry

Introduction, Elementary particles, and Relative masses

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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.

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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?

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Introduction Stoichiometry is the study of

the quantitative composition of chemical substances

the quantitative changes that take place during chemical reactions

2

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Atoms An atom is the smallest indivisible particle of

an element The “paper clip” analogy

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Atoms An atom is the smallest indivisible particle of

an element An atom is made up of 3 sub-atomic particles

-1e-

01n

+11p

electron

neutron

proton

Relative charge

Relative mass

SymbolParticle

01840

1

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Atoms The number of protons in an atom is called

atomic 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:

XAZChemical symbol

Mass number

Atomic number

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Atoms The number of protons in an atom is called

atomic 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:

Na2311 Be9

4 O168

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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

3

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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

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Atoms Atoms of the same element having different

mass numbers are called isotopes

Element Common isotopes

carbon

chlorine

hydrogen

C126 C13

6

Cl3517 Cl37

17

H11 H21 H31

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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.

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Atoms

192019

192119

172017

171817

Number of electrons

Number of neutrons

Number of protonsParticle

Cl3517

Cl3717

K4019

K3919

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Atoms

101211

1088

9214692

Number of electrons

Number of neutrons

Number of protonsParticle

U23892

2168O

Na2311

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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

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CStructure of ice (H2O)

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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

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Cl-

Na+

Ionic Compound Example: NaCl

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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

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Relative Mass To calculate relative mass:

Relative mass of a particle

mass of one particle

x mass of one 12C atom 12

1=

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Relative Isotopic Mass The relative isotopic mass

Mass of an isotope compared to the mass of a 12C atom

To calculate relative isotopic mass:


mass of one isotope


1=

12

1

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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:

12

1


average mass of one atom


1=

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Relative “Mango” mass Imagine inside your fridge you’ve got

Mangos from 3 different countries:

Mango Mass of mango / g Number in the fridge

China 12 3

Malaysia 10 2

Philipines 15 5

What is the average mass of the mangos?

Average mass of a mango

Total mass of mangos

Total number of mangos =

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China 12 3

Malaysia 10 2

Philipines 15 5


Average mass of a mango

(3 x 12) + (2 x 10) + (5 x 15)

3 + 2 + 5 =

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China 12 3

Malaysia 10 2

Philipines 15 5


Average mass of a mango 13.1 g=

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Relative Atomic Mass

An alternative equation:


(Relative abundance x relative isotopic mass)

(relative abundance) =

Sum up all the values contained in the set

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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

32

18731852(Re)

rA

= 186.2 (No units)

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Relative Atomic Mass

32

18731852(Re)

rA

= 186.2 Meaning:the average mass of one rhenium atom is 186.2 times heavier than the mass of a 12C atom

12

1

Example 1:Calculate the relative atomic mass of rhenium given that rhenium consist of two isotopes 185Re and 187Re in the ratio 2 : 3

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Relative Atomic Mass Example 2:

The abundance of the isotopes of chlorine are:

Calculate the relative atomic mass of chlorine

47.2453.75

97.3647.2497.3453.75)(

ClAr

= 35.46

Isotopes Relative isotopic mass % abundance35Cl 34.97 75.5337Cl 36.97 24.47

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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?

End of Lecture 1

Have a great weekend (Do review your notes)

the “zen” of tea-cups

Documents

mass nucleon number

unequal number of protons

elementan atom

different mass numbers

different mass numberatoms

smallest group of atoms

smallest indivisible

notes betternotes