The Structure of the Atom Chap. 4

I. History

A. Early Greeks Explain matter with 4 ‘elements’

I. History A. Early Greeks 1. Air 2. Earth 3. Fire 4. Water Explain matter with 4 ‘elements’

I. History A. Early Greeks B. Democritus Greek philosopher who first introduced concept of ‘atomos’

I. History A. Early Greeks B. Democritus C. Alchemists Devoted to making precious metals from base metals

Formulated the ‘Atomic Theory of Matter’ I. History A. Early Greeks B. Democritus C. Alchemists D. Dalton

Atomic Theory of Matter 1. All matter is made of...

Atomic Theory of Matter 1. All matter is made of Atoms cannot be...

Atomic Theory of Matter 1. All matter is made of Atoms cannot be Atoms of a given element...

Atomic Theory of Matter 1. All matter is made of Atoms cannot be Atoms of a given element Atoms of 2 different elements..

Atomic Theory of Matter 1. All matter is made of Atoms cannot be Atoms of a given element Atoms of different elements In a chemical reaction atoms are

I. History A. Early Greeks B. Democritus C. Alchemists D.Dalton E.Definition of Atom

Atom The smallest particle of an element that retains properties of that element.

Used a cathode ray tube (CRT) to measure the charge:mass ratio of an electron A.J.J. Thomson – 1890s II. Discoveries of atoms

A.J.J. Thomson – 1890s 1.chg:mass = 1.76 x C/kg

A.J.J. Thomson – 1890s 1.chg:mass = 1.76 x C/kg 2.Discovery led to plum-pudding model II. Discoveries of atoms

A.J.J. Thomson – 1890s B.Robert Millikan Measured the charge of an electron in his ‘oil drop’ exper. II. Discoveries of atoms

A.J.J. Thomson – 1890s B.Robert Millikan Charge = 1.6 x II. Discoveries of atoms

A.J.J. Thomson – 1890s B.Robert Millikan C.Rutherford Discovered nucleus in gold-foil experiment II. Discoveries of atoms

A.J.J. Thomson – 1890s B.Robert Millikan C.Rutherford Fired alpha particles at thin metal sheet. II. Discoveries of atoms

A.J.J. Thomson – 1890s B.Robert Millikan C.Rutherford Fired alpha particles at thin metal sheet. 2.Expected them to go straight through, but some deflected. II. Discoveries of atoms

A.J.J. Thomson – 1890s B.Robert Millikan C.Rutherford Fired alpha particles at thin metal sheet. 2.Expected them to go straight through, but some deflected. 3.This led to nuclear model. II. Discoveries of atoms

D.The atom II. Discoveries of atoms

D.The atom 1.The electron was discovered first II. Discoveries of atoms

D.The atom 1.The electron was discovered first 2.The proton was described by Rutherford II. Discoveries of atoms

D.The atom 1.The electron was discovered first 2.The proton was described by Rutherford 3.The neutron was described by Chadwick II. Discoveries of atoms

III. Representing Atoms What makes a carbon atom different from a nitrogen atom?

A.The atomic number III. Representing Atoms

A.The atomic number 1.The number of protons III. Representing Atoms

A.The atomic number 1.The number of protons 2.Written on the periodic table. III. Representing Atoms

A.The atomic number 1.The number of protons 2.Written on the periodic table. 3.This will equal the number of electrons, too. III. Representing Atoms

A.The atomic number B.The mass number III. Representing Atoms

A.The atomic number B.The mass number 1.The number of protons + neutrons III. Representing Atoms

A.The atomic number B.The mass number 1.The number of protons + neutrons 2.Always a whole number III. Representing Atoms

A.The atomic number B.The mass number C.Isotopes III. Representing Atoms

A.The atomic number B.The mass number C.Isotopes 1.Atoms with the same number of protons, different number of neutrons III. Representing Atoms

A.The atomic number B.The mass number C.Isotopes 1.Atoms with the same number of protons, different number of neutrons 2.Isotopes have same properties, but different masses III. Representing Atoms

A.The atomic number B.The mass number C.Isotopes D.Notation III. Representing Atoms

Cl Nuclide Symbol Notation

Cl Element symbol Nuclide Symbol Notation

Cl Atomic number Nuclide Symbol Notation

Cl Mass number Nuclide Symbol Notation

Self Check – Ex. 1 Write the nuclide symbols for elements with these particles: Nuclide #1 22 protons 24 neutrons Nuclide #2 22 protons 26 neutrons

Self Check – Ex. 2 How many protons, neutrons, and electrons are in this element? Mo 95 42

Self Check – Ex. 3 How many protons, neutrons, and electrons are in this element? K 40

IV. Mass of atoms

A.Measured in amu IV. Mass of atoms

A.Measured in amu B.Protons and neutrons both weigh about 1 amu (neutrons are a bit more) IV. Mass of atoms

A.Measured in amu B.Protons and neutrons both weigh about 1 amu (neutrons are a bit more) C.The amu is defined as 1/12 the mass of carbon-12 IV. Mass of atoms

V. Atomic Mass

A.A weighted average of all the isotopes for a given element V. Atomic Mass

The older pennies have a mass of 3.0 g while the newer pennies have mass of 2.5 g. What is the average mass of these pennies? An analogy

The older pennies have a mass of 3.0 g while the newer pennies have mass of 2.5 g. What is the average mass of these pennies? An analogy 5 older 5 newer

What is the average mass of this sample? There are 4 older pennies (3.0 g) while there are 10 newer pennies have mass of 2.5 g. An analogy 4 older 10 newer

The older pennies have a mass of 3.0 g while the newer pennies have mass of 2.5 g. What is the average mass of these pennies? An analogy older newer

A.A weighted average of all the isotopes for a given element B.Formula V. Atomic Mass

% Isotope #1 x Mass of isotope #1 Atomic Mass % Isotope #2 x Mass of isotope #2 % Isotope #3 x Mass of isotope #3 + + all other isotopes + Atomic mass =

Self Check – Ex. 4 Use the following to find the atomic mass for chlorine. Chlorine % amu Chlorine % amu

VI. Radioactive Decay

A.Some atoms spontaneously emit radiation VI. Radioactive Decay

A.Some atoms spontaneously emit radiation B.Atoms change their identities in the process VI. Radioactive Decay

A.Some atoms spontaneously emit radiation B.Atoms change their identities in the process C.Atoms undergo radioactive decay because their nuclei are unstable VI. Radioactive Decay

VII. Types of Radiation

A.Alpha radiation VII. Types of Radiation

A.Alpha radiation VII. Types of Radiation 1.Make unstable heavy nuclei lighter

A.Alpha radiation VII. Types of Radiation 1.Make unstable heavy nuclei lighter 2.This radiation is attracted to negative electric fields

A.Alpha radiation VII. Types of Radiation 1.Make unstable heavy nuclei lighter 2.This radiation is attracted to negative electric fields 3.Comprised of alpha particles

Alpha Particles Made of: 2 protons & 2 neutrons Charge: Mass: Symbol:

Alpha Particles Made of: 2 protons & 2 neutrons Charge: Mass: Symbol: 2 +

Alpha Particles Made of: 2 protons & 2 neutrons Charge: Mass: Symbol: amu

Alpha Particles Made of: 2 protons & 2 neutrons Charge: Mass: Symbol: amu He 4 2 α 4 2 or

B.Beta radiation VII. Types of Radiation

B.Beta radiation VII. Types of Radiation 1.Increases the proton to neutron ratio

B.Beta radiation VII. Types of Radiation 1.Increases the proton to neutron ratio 2.Radiation is attracted to positive electric field

B.Beta radiation VII. Types of Radiation 1.Increases the proton to neutron ratio 2.Radiation is attracted to positive electric field 3.Comprised of beta particles

Beta Particles Made of: An electron from the nucleus Charge: Mass: Symbol:

Beta Particles Made of: An electron from the nucleus Charge: Mass: Symbol: 1 -

Beta Particles Made of: An electron from the nucleus Charge: Mass: Symbol: 1 - 1/1840 amu

Beta Particles Made of: An electron from the nucleus Charge: Mass: Symbol: 1 - 1/1840 amu e-e- 0 β 0 or

C.Gamma radiation VII. Types of Radiation

C.Gamma radiation VII. Types of Radiation 1.These accompany alpha and beta radiation

C.Gamma radiation VII. Types of Radiation 1.These accompany alpha and beta radiation 2.Not deflected by electric field

C.Gamma radiation VII. Types of Radiation 1.These accompany alpha and beta radiation 2.Not deflected by electric field 3.Gamma rays are high energy radiation

Gamma Particles Made of: Energy (not matter) Charge: Mass: Symbol: none γ 0 0

VIII. Penetrating Ability

A.Alpha radiation penetrates the. VIII. Penetrating Ability

A.Alpha radiation penetrates the least. B.Gamma radiation penetrates the. VIII. Penetrating Ability

A.Alpha radiation penetrates the least. B.Gamma radiation penetrates the most. VIII. Penetrating Ability

IX. Writing Equations

A.Atomic numbers and mass numbers are conserved IX. Writing Equations

A.Atomic numbers and mass numbers are conserved B.Examples IX. Writing Equations

Self Check – Ex. 5 Complete the following nuclear equation. K Ca + ? K Ca + ?

Self Check – Ex. 6 Complete the following nuclear equation. Pu ? + α Pu ? + α