1 Atomic Structure and Relative Masses 1.1The Atomic Nature of Matter 1.2The Experimental Evidence...

Atomic Structure Atomic Structure and Relative Massesand Relative Masses

1.11.1 The Atomic Nature of MatterThe Atomic Nature of Matter

1.21.2 The Experimental Evidence of Atomic StructureThe Experimental Evidence of Atomic Structure

1.31.3 Sub-atomic ParticlesSub-atomic Particles

1.41.4 Atomic Number, Mass Number and IsotopesAtomic Number, Mass Number and Isotopes

1.51.5 Mass SpectrometerMass Spectrometer

1.61.6 Relative Isotopic, Atomic and Molecular MassesRelative Isotopic, Atomic and Molecular Masses

1.1.11 The Atomic The Atomic

Nature of Nature of MatterMatter

What is “atom”?What is “atom”?

1.1 The atomic nature of matter (SB p.2)

The Greek philosopher Democritus (~460 B.C. – 370 B.C.)

Atomos = indivisibleAtomism(原子論 )

Continuous division

These are iron atoms!!

Atomos = indivisible

Atomos = indivisible管子 <內業篇 >靈氣在心，一來一逝，其細無內，其大無外

Dalton’s atomic Dalton’s atomic theorytheory1803 AD John Dalton

Main points of Dalton’s atomic Main points of Dalton’s atomic theorytheory1. All elements are made up of atoms.

2. Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process.

A chemical reaction simply changes the way atoms are grouped together.

Main points of Dalton’s atomic Main points of Dalton’s atomic theorytheory

5. When atoms of different elements combine to form a compound, they do so in a simple whole number ratio to each other.

3. Atoms of the same element are identical. They have the same mass and chemical properties.

4. Atoms of different elements are different. They have different masses and chemical properties.

Check Point 1-1Check Point 1-1

The The Experimental Experimental Evidence of Evidence of

Atomic Atomic StructureStructure

1.1.22

1.2 The experimental evidence of atomic structure (SB p.3)Steps to Thomson’s Atomic Steps to Thomson’s Atomic

ModelModel

•1876 Goldstein

Discovery of cathode rays from discharge tube experiment.

Discovery of Cathode RaysDiscovery of Cathode Rays

• A beam of rays came out from the cathode and hit the anode

• Goldstein called the beam cathode rays

1.2 The experimental evidence of atomic structure (SB p.3)

Steps to Thomson’s Atomic Steps to Thomson’s Atomic ModelModel

•1876 Goldstein

Discovery of cathode rays from discharge tube experiment.

•1895 Crookes

Cathode rays are negatively charged particles which travelled in straight line. electrons

Deflected in the electric

Deflected in the magnetic

The beam was composed of negatively charged fast-moving particles.

Measurement of the m/e ratio of Measurement of the m/e ratio of ‘electron’‘electron’

J J Thomson (1856-1940)

Measure the mass to charge ratio (m/e) of the particles produced

Independent of the nature of the gas inside the discharge tube

The particles were constituents of all atoms!!

Thomson called the particles ‘electrons’.

Thomson’s atomic Thomson’s atomic modelmodel

• An atom was a positively charged sphere of low density+ +

• The positively charged sphere is balanced electrically by negatively charged electrons

Electron

How are the particles distributed How are the particles distributed in an atom?in an atom?

Positive charge

• Most of the mass of the atom was carried by the electrons (>1000 e-)

Electron

• An atom was a positively charged sphere of low density with negatively charged electrons embedded in it like a plum pudding

Positive charge

Like a raisin bun ( 提子飽 )

Electron

Experimental evidence : -

Powerful projectiles such as -particles passes straight through a thin gold foil.

Analogy : -

-particle vs a thin gold foil

15-inch canon ball vs a piece of paper

Steps to Rutherford’s Atomic Steps to Rutherford’s Atomic ModelModel

•Nobel laureates, Physics, 1903

Becquerel Marie Curie

Pierre Curie

•1896 Becquerel

1st discovery of radioactive substance.

(an uranium salt)

Steps to Rutherford’s Atomic Steps to Rutherford’s Atomic ModelModel•1898 Pierre & Marie Curie

Radioactive polonium and radium were isolated

1g from 500 Kg pitchblende

The Curie FamilyThe Curie Family

•Pierre & Marie Curie

Nobel laureate, Physics, 1903•Marie Curie

Nobel laureate, Chemistry, 1911•Federic Joliet & Irene Joliet-Curie

Nobel laureate, Chemistry, 1935

•1899 Rutherford

(Nobel laureate, Physics, 1908)

Discovery of and radiations.

radiation He2+

radiation e

Rutherford’s scattering Rutherford’s scattering experimentexperiment

• A thin gold foil was bombarded with a beam of fast-moving -particles (+ve charged)

Observation:

• most -particles passed through the foil without deflection

• very few -particles were scattered or rebounded back

It was quite the most incredible event that has ever happened to me in my life.

It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.

Interpretation of the experimental resultsInterpretation of the experimental results

• Nucleus is positively charged because it repels the positively charged alpha particles.

• Nucleus occupies a very small space (10-

12 of size of atom) because very few particles are deflected.

• The radius of an atom is about 20,000 times that of the nucleus. Thus, if we imagine a large football stadium as being the whole atom, then the nucleus would be about the size of a peanut.

• Nucleus is relatively massive and highly charged because of the large deflection.

Presence of protons in nucleus

• Number of positive charges in each nucleus can be calculated from experimental results

Steps to Chadwick’s Atomic Steps to Chadwick’s Atomic ModelModel

Ne2010 Ne22

• 1919 F. W. Aston

(Nobel laureate, Chemistry, 1922)

Isotopes of Neon were discovered using mass spectrometry

• 1920 Rutherford

Postulated the presence of neutrons in the nucleus

• James Chadwick

(Nobel laureate, Physics, 1935)

Discovery of the neutron

Chadwick’s ExperimentsChadwick’s Experiments

Be94 He4

2 C126

n10+ +

Interpretation : -

Chadwick’s atomic Chadwick’s atomic modelmodel

ProtonElectron

Neutron Check Point Check Point 1-21-2

Sub-atomic Sub-atomic ParticlesParticles

1.1.33

Sub-atomic particlesSub-atomic particles

1.3 Sub-atomic particles (SB p.6)

3 kinds of sub-atomic particles:

• Protons

• Neutrons

• Electrons

Inside the condensed nucleus

Moving around the nucleus

A carbon-12 atomA carbon-12 atom

Characteristics of sub-atomic Characteristics of sub-atomic particlesparticles

Sub-atomic particle

Proton Neutron Electron

Symbol p or n or e- or

Location in atom

Nucleus Nucleus Surrounding the nucleus

Actual charge (C)

1.6 10-9 0 1.6 x 10-9

Relative charge

+1 0 -1

Actual mass (g)

1.7 10-24 1.7 10-24 9.1 10-28

Approximate relative mass (a.m.u.)

H11 n1

1 a.m.u. = 1/12 of the mass of a C-12 atom

mass of a C-12 atom 6p + 6n

mass of p mass of n 1 a.m.u.

One C-12 atom has 6 p, 6n and 6e

mass of p mass of n

mass of e can be ignored

mass of a C-12 atom 6p + 6n 12p 12n

Express the masses of the following isotopes in a.m.u..

C146C13

~13 ~14

Atomic Atomic Number, Number,

Mass Mass Number and Number and

IsotopesIsotopes

1.1.44

Atomic numberAtomic number1.4 Atomic number, mass number and isotopes (SB p.7)

The atomic number (Z) of an element is the number of protons contained in the nucleus of the atom.

Atomic number =

Number of protons

Number of electrons=

Atoms are electrically neutral

Mass numberMass number

1.4 Atomic number, mass number and isotopes (SB p.8)

The mass number (A) of an atom is the sum of the number of protons and neutrons in the nucleus.

Mass number

= Number of protons

Number of neutrons

Number of neutrons = Mass number – Atomic number

IsotopesIsotopes

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. Or

Isotopes are atoms of the same element with the same atomic number but different mass numbers

Notation for an isotope

Symbol of the

element

Mass number

Atomic number

Atomic numbe

Mass number

Number of

protons

No. of electron

No. of neutron

Notation

28 14 14

22 10 10

34 34 34

30 30 36

Si2814

Ne2210

Se7834

Zn6630

A boron isotope has a relative mass of ~10 a.m.u.

Give the isotopic notation.

Discovery of isotopes by mass Discovery of isotopes by mass spectrometryspectrometry

What is the difference in mass between the two isotopes of hydrogen ?

H11 H2

1 a.m.u.

= 1.7 10-24 g

= 0.0000000000000000000000017 g

No balance is accurate enough to distinguish this difference

What is the relative abundances of the two isotopes of hydrogen ?

H11 H2

99.8% 0.02%

Both tasks can be accomplished with a mass spectrometer !!

What is the difference in mass between the two isotopes of hydrogen ?

1.5 Mass spectrometer (SB p.10)

Mass spectrometerMass spectrometer

Extremely accurate

Resolution :

1024 g

Highly preciseResults of measurement are reproducible

Highly sensitive

Sample size : as small as 1 g

Highly efficient

Analysis can be accomplished in a couple of minutes.

The sample (element or compound) is vaporized

Positive ions are produced from the vapour

X(g) + e X+(g) + 2e

Atom Simple ionMolecule Molecular/polyatomic ion

+ve ions accelerated by a known and fixed electric field

+ve ions are then deflected by a known and variable magnetic field

The ions are detected

The mass spectrum is traced out by the recorder

Mass spectrum of Rb:Mass spectrum of Rb:

x-axis :-

For singly charged ions, e = 1

m/e = m

= isotopic mass (relative to C-12)

mass number (whole number)

Relative isotopic massRelative isotopic mass

The relative isotopic mass of a particular isotope of an element is the relative mass of one atom of that isotope on the 12C = 12.0000 scale.

Mass spectrum of Rb:Mass spectrum of Rb:

Y-axis :-

Relative abundance,

Ion intensity, or

Detector current

Relative atomic massRelative atomic mass

The relative atomic mass of an element is the weighted average of the relative isotopic masses of the natural isotopes on the 12C = 12.0000 scale.

Q.172.12%

27.88%

Relative atomic mass of Rb

= 85 72.12% + 87 27.88%

= 85.56

1.9 Relative isotopic, atomic and molecular masses (SB p.22)

The mass spectrum of lead is given below. Given that the relative atomic mass of lead is 207.242, calculate the relative abundance of the peak at m/e of 208.

x47.7x

208x47.7

22.6207

x47.723.6

206x47.7

1.5204 207.242

Let x be the relative abundance of the peak at m/e of 208

x = 52.3

Q.2(a)

Relative atomic mass of Pb

)105.2

(208)()102.2

(207)()102.4

(206)()100.2

(204)(

= 207.2

Q.2(b) 103

2206Pb

2208Pb

Q.3(a)(i)/(ii)

The lighter ions(220Rn+) with a smaller m/e ratio are defected more

the strength of the magnetic field or

the strength of the electric field would bring the ions from Y onto the detector.

In practice, the strength of the electric field is fixed while that of the magnetic field is increased gradually to bring ions of increasing m/e ratios onto the detector.

Rn2+ would be deflected more than the ions at X and Y. (Rn2+ has a smaller m/e)

If magnetic field strength and electric field strength are fixed,

m/e deflection

m/eRelative

abundance

Ionic species

14 4.0

16 0.8

20 0.3

28 100

29 0.76

N]N[ 1414

N]N[ 1514

21414 N]N[

21616 O]O[

m/eRelative

abundance

Ionic species

33 0.02

34 0.09

40 2.0

44 0.10

O]O[ 1616

O]O[ 1716

O]O[ 1717

O]CO[ 161216

Relative molecular Relative molecular massmass

The relative molecular mass is the relative mass of a molecule on the carbon-12 scale.

Relative molecular mass can be determined by mass spectrometer directly.

Mass spectrum of Mass spectrum of ClCl22:: The peaks with higher m/e ratio

correspond to molecular ions

Fragmentation of molecules always occurs during the ionization process.

Cl2(g) Cl(g) + Cl(g)

Mass spectrum of Mass spectrum of ClCl22::

The scale has been enlarged for these two peaks.

Complete the following tableComplete the following table

m/e ratio

Corresponding ion

[35Cl-35Cl]+

[35Cl-37Cl]+

[37Cl-37Cl]+

What is the relative atomic mass of Cl?What is the relative atomic mass of Cl?The relative abundances

of Cl-35 and Cl-37 are 75.77 and 24.23

respectively

10024.23

75.7735 RAM

= 35.48

What is the relative molecular mass of What is the relative molecular mass of ClCl22 ? ?

Method 1 70.96 35.482 RMM

Method 2

744818

724827

70 RMM

What is the RMM of CHWhat is the RMM of CH33Cl?Cl?

521652

51165123

50 RMM

= 50.50

Molecular ions

Complete the following tableComplete the following table

m/e Corresponding ion

[12C1H335Cl]+

[12C1H337Cl]+

[13C1H335Cl]+ , [12C2H1H2

35Cl]+

The mass spectrum of dichloromethane is given below. Calculate the relative molecular mass of dichloromethane.

174.50.8

90174.52.5

89174.5

174.52.2

87174.5

174.53

85174.5

9484 RMM

= 85.128

The END

(a)What does the word “atom” literally mean?

(b)Which point of Dalton’s atomic theory is based on the law of conservation of mass proposed by Lavoisier in 1774 which states that matter is neither created nor destroyed in the course of a chemical reaction?

(c)Which point of Dalton’s atomic theory is based on the law of constant proportion proposed by Proust in 1799 which states that all pure samples of the same chemical compound contain the same elements combined together in the same proportions by mass?

(a) Indivisible

(b) Atoms can neither be created nor destroyed.

(c) Atoms of different elements combine to form a compound. The numbers of various atoms combined bear a simple whole number ratio to each other.

Answer

(a)Atoms were found to be divisible. What names were given to the particles found inside the atoms?

(b)Give the most important point of the following experiments:

(i) E. Goldstein’s gas discharge tube experiment;

(ii) J. J. Thomson’s cathode ray tube experiment;

(iii) E. Rutherford’s gold foil scattering experiment.

1.2 The Experimental evidence of atomic structure (SB p.4)

(a) Electron, proton and neutron

(b) (i) Discovery of cathode rays

(ii) Discovery of electrons

(iii) Discovery of nucleus in atoms

Answer

The identity of an element is determined by the number of which sub-atomic particle?

The identity of an element is determined by the number of protons in its atomic nucleus.

Answer

(a)Which part of the atom accounts for almost all the mass of that atom?

(b) The mass of which sub-atomic particle is often assumed to be zero?

1.3 Sub-atomic Particles (SB p.7)

(a) Nucleus

(b) Electron

Answer

Are there any sub-atomic particles other than protons, neutrons and electrons?

Other than the three common types of sub-atomic particles (proton, neutron and electron), there are also some sub-atomic particles called positron (anti-electron) and quark.

Answer

If bromine has two isotopes, 79Br and 81Br, how many physically distinguishable combinations of Br

atoms are there in Br2?

79Br—79Br

79Br—81Br

81Br—81Br

They have different molecular masses and thus have

different density

Write the symbol for the atom that has an atomic number of 11 and a mass number of 23. How many protons, neutrons and electrons does this atom have?

, 11 protons, 12 neutrons, 11 electrons.Na23

Answer

Label the different parts of the mass spectrometer.

A – Vaporization chamber

B – Ionization chamber

C – Accelerating electric field

D – Deflecting magnetic field

E – Ion detector

Answer

The mass spectrum of neon is given below. Determine the relative atomic mass of neon.

Relative atomic mass of neon

= 20.18

)2.112.0114()2.1122()2.021()11420(

Answer

(a) The mass spectrum of lead is given below. Given that the relative atomic mass of lead is 207.242, calculate the relative abundance of the peak at m/e of 208.

Let x be the relative abundance of the peak at m/e of 208.

(204 1.5 + 206 23.6 + 207 22.6 + 208x) (1.5 + 23.6 + 22.6 + x) = 207.242

x = 52.3

The relative abundance of the peak at m/e of 208 is 52.3.

Answer

(b) The mass spectrum of dichloromethane is given below. Calculate the relative molecular mass of dichloromethane.

The relative molecular mass of dichloromethane

= (84 94 + 85 3.0 + 86 59 + 87 2.2 + 88 13 + 89 2.5 + 90 0.8) (94 + 3.0 + 59 + 2.2 + 13 + 2.5 + 0.8)

= 85.128

The relative molecular mass of dichloromethane is 85.128.

Answer

1 Atomic Structure and Relative Masses 1.1The Atomic Nature of Matter 1.2The Experimental Evidence...

Documents

ATOMIC STRUCTURE. INVESTIGATION 1 Atomic Structure

Atomic Structure and Atomic Spectra

Atomic Mass and Atomic Number Worksheet

Atomic Absorption and Atomic Fluorescence Spectroscopy

Atomic History & Atomic Structure!

IB Chemistry 1: Topic 2 Atomic Structure: atomic particles, atomic number, mass #, isotopes and atomic mass

Atomic Structure and Atomic Spectra · 2018. 1. 30. · Atomic spectroscopy: experimental technique to determine the electronic structure of atoms Atomic Structure and Atomic Spectra

Topic 10 – Strategic Logistics Planning Outline 1.1What is Strategic Planning? 1.2The Importance of Planning 1.3The Corporate Planning Process

2.0 - Strategic Procurement Divisionpurchasing.houstontx.gov/bids/T24541/S17-T24541... · Web view1.0Background. 1.1The Police Department (HPD) wishes to consider proposals for

Welcome to Atomic Physics! | Atomic Physics

New Way Chemistry for Hong Kong A-Level Book 11 Atomic Structure, Radioactivity and Relative Masses 1.1The Atomic Nature of Matter 1.2The Experimental

INTERNATIONALhobieclass.com/wp-content/uploads/2015/09/HTIG_CR_1… · Web viewA.1.2The word “shall” is mandatory and the word ... after having received the International

ATOMIC SPECROSCOPY (AS) Atomic Absorption Spectroscopy Flame Atomic Emission Spectroscopy ICP Atomic Emission Spectroscopy

Scandium Sc Atomic Number: 21 Atomic Mass: 44.955910 Atomic Number: 21 Atomic Mass: 44.955910

New Way Chemistry for Hong Kong A-Level Book 11 Atomic Structure 1.1The Atomic Nature of Matter 1.2The Experimental Evidence of Atomic Structure Atomic

Atomic Absorption & Atomic Emission Spectroscopy

ATOMIC STRUCTURE REVIEW AND HISTORY OF THE ATOMIC MODEL Atomic Theory

What’s in my atom? Protons = atomic number Electrons = atomic number Neutrons = relative atomic mass –. atomic number Sub-atomic particles Atoms are made

Atomic Spectroscopy: Atomic Emission Spectroscopy Atomic Absorption Spectroscopy Atomic Fluorescence Spectroscopy * Elemental Analysis * Sample is atomized

Periodic Trends Trends in Atomic Size Atomic Size (Atomic Radius): The atomic size of an atom, also called the atomic radius, refers to the distance between