Atoms and Atomic Structure

Atoms and Atomic Structure : 

Atoms and Atomic Structure

Law of Conservation of MassLavoisier (1743-1794) : 

Law of Conservation of MassLavoisier (1743-1794) In a chemical reaction, matter is neither created nor destroyed. P. 57 Click on picture for movie

Slide 3: 

CuCO3(s)  CuO(s) + CO2(g) 123.6 g 79.6 g ? g

Slide 4: 

CuCO3(s)  CuO(s) + CO2(g) 123.6 g 79.6 g 44.0 g

Slide 5: 

CuCO3(s)  CuO(s) + CO2(g) 123.6 g 79.6 g 44.0 g 123.6 g 79.6 g + 44.0 g =

Law of Definite ProportionsProost (1754-1826) : 

Law of Definite ProportionsProost (1754-1826) Different samples of any pure compound contain the same elements in the same proportions by mass. P. 58

Slide 7: 

Mass Ratio of Cu:O:C in copper carbonate Cu:O:C = 53:40:10 = 5.3 : 4: 1 Regardless of where the copper carbonate is found

Slide 8: 

Mass Ratio of Cu:O:C in copper carbonate Cu:O:C = 53:40:10 = 5.3 : 4: 1 If a sample of copper carbonate contains 20 g of carbon how many g of Cu will it contain?

Slide 9: 

Mass Ratio of Cu:O:C in copper carbonate Cu:O:C = 53:40:10 = 5.3 : 4: 1 If a sample of copper carbonate contains 20 g of carbon how many g of Cu will it contain? Cu / C = 5.3g / 1g = x / 20g

Slide 10: 

Mass Ratio of Cu:O:C in copper carbonate Cu:O:C = 53:40:10 = 5.3 : 4: 1 If a sample of copper carbonate contains 20 g of carbon how many g of Cu will it contain? (5.3g / 1g)20g = x

Slide 11: 

Mass Ratio of Cu:O:C in copper carbonate Cu:O:C = 53:40:10 = 5.3 : 4: 1 If a sample of copper carbonate contains 20 g of carbon how many g of Cu will it contain? 106 g = x

Law of Multiple Proportions (John Dalton) : 

Law of Multiple Proportions (John Dalton) The masses of one element that can combine chemically with a fixed mass of another element are in a ratio of small whole numbers. 2C + O2  2CO Carbon monoxide C + O2  CO2 Carbon dioxide P. 59 24 g 32 g 12 g 32 g 2:1

The idea of “whole numbers” suggests the presence of “individual” particleATOMS ! : 

The idea of “whole numbers” suggests the presence of “individual” particleATOMS !

Dalton’s Atomic Theory : 

Dalton’s Atomic Theory John Dalton (1766-1844) proposed an atomic theory matter is composed, indivisible particles (atoms). all atoms of a particular element are identical different elements have different atoms atoms combine in certain whole-number ratios In a chemical reaction, atoms are merely rearranged to form new compounds; they are not created, destroyed, or changed into atoms of any other elements. P. 56-57

OK! Matter is made of ATOMSBut what are ATOMS?What are ATOMS themselves made of? : 

OK! Matter is made of ATOMSBut what are ATOMS?What are ATOMS themselves made of?

Cathode–Ray Tube : 

Cathode–Ray Tube P. 61

J.J. Thompson (1856-1940) : 

J.J. Thompson (1856-1940)

Cathode Rays - JJ Thompson : 

Cathode Rays - JJ Thompson P. 62

Mass of an electron : 

Mass of an electron Experiments performed by Thompson together with those of Robert Millikan were able to show that an electron has a mass of 9.1 x 10-28 g The mass of one atom of the lightest element, hydrogen, is 1.7 x 10-24 g An electron is approx 1/2000th the mass of a H atom!

So the electron appears to be an insignificant part of the atom - from a mass point of view!How are electrons arranged inside an atom? : 

So the electron appears to be an insignificant part of the atom - from a mass point of view!How are electrons arranged inside an atom?

Thompson’s Plum Pudding Model of the Atom : 

Thompson’s Plum Pudding Model of the Atom electron Diffuse positive charge

Slide 22: 

Ernest Rutherford (1871-1937)

Nucleus of the AtomRutherford (1871-1937) : 

Nucleus of the AtomRutherford (1871-1937) P. 64 Click on picture for movie

Nucleus of the Atom Continued : 

Nucleus of the Atom Continued P. 64

Nucleus of the Atom Continued (Rutherford) : 

Nucleus of the Atom Continued (Rutherford) At the center of the atom is a very dense nucleus that accounts for almost all the mass of the atom and contains all the positive charge. He named these positive particles protons. Protons have a relative mass of 1 and a charge of +1. P. 64

Nucleus of the AtomChadwick (1891-1974) : 

Nucleus of the AtomChadwick (1891-1974) When atoms of beryllium were bombarded with alpha particles, new uncharged particles with mass identical to protons were emitted. These uncharged particles were called neutrons. Neutrons have a relative mass of 1 and a charge of zero. P. 64-65

Characteristics of the Three Basic Subatomic Particles : 

Characteristics of the Three Basic Subatomic Particles P. 65

Arrangement of Subatomic Particles in the Atom : 

Arrangement of Subatomic Particles in the Atom P. 66

Atoms are mainly EMPTY SPACE ! : 

Atoms are mainly EMPTY SPACE !

Slide 33: 

And so are ALL OF US !

Slide 34: 

Our first direct look at the atomic world Get me out of here!

Slide 35: 

View of Atoms from STM

Slide 36: 

Scanning Tunneling Microscopy

Isotopes : 

Isotopes Atoms of an element that have the same number of protons but different numbers of neutrons are called isotopes. AX X = symbol of element Z A = mass number Z = atomic number The isotopes of sulfur are written: 32 S 33 S 34 S 36 S 16 16 16 16

Isotopes Continued : 

Isotopes Continued Which of the following represent isotopes of the same element? Which element? 234 X 234 X 235 X 238 X 92 93 92 92

Answer: : 

Answer: 234 U 234 Np 235 U 238 U 92 93 92 92 234 Np is not an isotope of Uranium. 93

Isotopes of Carbon : 

Isotopes of Carbon 12 C 13 C 14 C 6 6 6

Slide 42: 

12 C 13 C 14 C 6 6 6 12 - 6 = 6 neutrons 13 - 6 = 7 neutrons 14 - 6 = 8 neutrons Radioactive Isotopes of Carbon

Carbon-14 Dating : 

Carbon-14 Dating Used to date archeological artifacts up to 60000 years old measures amount of radioactive 14C left in a sample Amount of 14C decreases with time will be discussed in detail in Ch 5

Isotopic Fingerprinting : 

Isotopic Fingerprinting The ratio of stable isotopes (e.g. 13C/12C) in a substance will vary slightly depending on the origin of the substance for example, petroleum samples from different parts of the world will have different 13C/12C ratios How could such information be useful?

Time for some nuclear chemistry…let’s begin Ch 5 : 

Time for some nuclear chemistry…let’s begin Ch 5

Periodic TableMendeleev (1834-1907) : 

Periodic TableMendeleev (1834-1907) Atoms arranged by ascending atomic number Horizontal rows called periods Vertical columns called groups Elements within a group have similar chemical properties

The Periodic Table : 

The Periodic Table

Properties of Alkali Metals and Halogens : 

Properties of Alkali Metals and Halogens

Metals : 

Metals Metals have distinctive properties Good conductors of heat and electricity Shiny appearance Ductile and malleable Are light purple in periodic table that is on the inside cover of the book

Nonmetals : 

Nonmetals Do not conduct heat or electricity Not ductile or malleable Many exist as gases Are green in periodic table that is on the inside cover of the book

Semimetals : 

Semimetals Have properties that lie between those of metals and nonmetals Are gold yellow in the periodic table that is on the inside cover of the book

REFERENCE : 

REFERENCE www.langara.bc.ca/chemistry/A_Mosi/C1117_Ch3.ppt