The Atom

I. Elements A. Are Pure substances made of only one kind of atomPure substances made of only one kind of atom

An element is a substance made up of a single type of atom.

O46.6 % Si27.7 Al 8.1 Fe 5.0 Ca 3.6 Na2.8 % K2.6 Mg2.1 Ti0.4 H0.1 I. Elements B. The Earth’s Ten Most Abundant Elements

II. THE ATOM A.What is An Atom? 1.An atom is the smallest particle of an element that still has the properties of that element

II. THE ATOM 1.The Greek Philosophers 1.The Greek Philosophers (500 B.C.) originated the concept of the atom. Atomos = uncuttable B. How the Atom was “Discovered” B. How the Atom was “Discovered”

2. The Dark Ages The study of science was all but lost B. How the Atom was “Discovered” B. How the Atom was “Discovered”

B. How the Atom was “Discovered” 3. John Dalton ( ) –Renewed the concept of the atom –His model of the atom resembled that of a billiard ball - a small, solid sphere

B.How the Atom was “Discovered” 3. John Dalton ( ) Dalton’s Atomic Theory Atoms are indivisible Atoms are uniformly dense solid spheres Atoms of the same element are alike Atoms of different elements are different

B. How the Atom was “Discovered” J.J. Thomson 4. J.J. Thomson ( ) *“Discovered” the electron “Plum Pudding”Proposed the “Plum Pudding” model of the Atom  Plums = electrons  Pudding = sea of protons Explained the electrical properties of an atom

B. How the Atom was “Discovered” 5. Rutherford ( ) discovered the nucleus put p + in the nucleus and the e - outside the nucleus

B. How the Atom was “Discovered” 5. Bohr ( ) Electrons assume only certain orbits around the nucleus like planets around the sun. Each orbit has an energy associated with it.

B. How the Atom was “Discovered” 6. The Modern Model Quantum Mechanical Model or Electron Cloud Model Based on a Mathematical formula Predicts where e- are 90% of time

The cloud model represents a sort of history of where the electron has probably been and where it is likely to be going.

III. INSIDE THE ATOM A. The Nucleus 1. center of atom 2. positively charged (+) 3. gives the atom its mass 4. contains Protons symbol p +Protons symbol p + + chg mass = 1 amu Neutrons symbol n oNeutrons symbol n o 0 chgmass = 1 amu

III. INSIDE THE ATOM B. Energy Levels 1. surround the nucleus 2. negatively charged (-) 3. contains Electrons symbol e -Electrons symbol e - (-) chg mass = 0 amu

If the proton and neutron were enlarged, and each had the approximate mass of a hippopotamus, the electron, enlarged to the same scale, would have less mass than an owl.

III. INSIDE THE ATOM C. Atoms are Electrically Neutral 1. # protons = # electrons 2. Example: Sodium has 11 p e - total charge 0

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton Neutron Electron Complete the chart below:

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ Neutron Electron

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ 1 amu Neutron Electron

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ 1 amu +1 Neutron Electron

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ 1 amu +1 Nucleus Neutron Electron

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ 1 amu +1 Nucleus Neutron n0n0 Electron

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ 1 amu +1 Nucleus Neutron n0n0 1 amu Electron

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ 1 amu +1 Nucleus Neutron n0n0 1 amu 0 Electron

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ 1 amu +1 Nucleus Neutron n0n0 1 amu 0 Nucleus Electron

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ 1 amu +1 Nucleus Neutron n0n0 1 amu 0 Nucleus Electron e-e-

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ 1 amu +1 Nucleus Neutron n0n0 1 amu 0 Nucleus Electron e-e- 0 amu

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ 1 amu +1 Nucleus Neutron n0n0 1 amu 0 Nucleus Electron e-e- 0 amu

REVIEW IT NOW! ParticleSymbolMassChgLocation Proton p+p+ 1 amu +1 Nucleus Neutron n0n0 1 amu 0 Nucleus Electron e-e- 0 amu Around nucleus

III. INSIDE THE ATOM D. Quarks 1.Protons and neutrons are made of smaller particles called quarks Up quarks and Down quarks Quarks are held together by gluons 2.Electrons are not made of smaller particles

u d d d d d u u u u u d u

IV. Atomic Number, Mass Number and Isotopes A. Atomic Number 1. protons 1. Is the number of protons 2. # protons determines the identity of the atom 3. Remember # p + = # e - 4. You can get # p + from the periodic table

11 Na Sodium Atomic Number Atomic Symbol Atomic Name Atomic Mass (Average)

B. Mass Number 1.Mass Number = Protons + Neutrons 2. Examples Sodium # protons = 11 # neutrons = 12 mass number = ? 23

B. Mass Number 2. Examples Boron atomic number = 5 mass number = 11 ? number of neutrons = ? 6

1.WHAT ELEMENT IS THIS AN ATOM OF? 2.WHAT IS THE ATOMIC NUMBER OF THIS ATOM 3.WHAT IS THE MASS NUMBER OF THIS ATOM? YOUR TURN: 1. Sc

4.WHAT ELEMENT IS THIS AN ATOM OF? 5.WHAT IS THE ATOMIC NUMBER OF THIS ATOM 6.WHAT IS THE MASS NUMBER OF THIS ATOM? YOUR TURN: 4. K

7.WHAT ELEMENT IS THIS AN ATOM OF? 8.WHAT IS THE ATOMIC NUMBER OF THIS ATOM 9.WHAT IS THE MASS NUMBER OF THIS ATOM? YOUR TURN: 7. Cs

YOUR TURN COMPLETE THE CHART # P# E# NMASS # Mn 25 30? F? 99? Al 13?? 27 K? 19?

The Atomic Mass on the Periodic Table is the Average Mass – If you round the mass number to a whole number then you can calculate the # of neutrons in the most common atoms of the element. Ex. Na = Rounds to 23

Determine the following about the most common atom of gold: A. Symbol B. Atomic Number C. Mass Number D. Number of Protons E. Number of Electrons F. Number of Neutrons Au

C. Isotopes 1.Are atoms of the same element with different numbers of neutrons 2.Example What is the mass # ? –Some atoms of boron have 6 neutrons. What is the mass # ?11

C. Isotopes 2.Example What is the mass #? –Some boron atoms have 5 neutrons. What is the mass #?10

Check Your Understanding –Atom A has 15 protons and 17 neutrons –Atom B has 18 protons and 17 neutrons Are the atoms isotopes or are they atoms of different elements? different elements

C. Isotopes 3. Names and Symbols of Isotopes Include the element name or symbol and mass # ExampleExample What is the name and symbol of this isotope? Some atoms of boron have 6 neutrons. What is the name and symbol of this isotope? Boron B 5

D. 3 Laws of Chemistry A. The Law of the Conservation of Mass Mass In any chemical reaction, matter (and therefore mass) is neither created or destroyed.

D. 3 Laws of Chemistry A. The Law Definite Proportions In any like chemical compound, atoms always combine in definite proportions. ex. molecules of water always contain 2 hydrogen atoms and 1 oxygen 2 hydrogen atoms and 1 oxygen atom atom

D. 3 Laws of Chemistry A. The Law Multiple Proportions Atoms can combine in different ratios to create different compounds. ex. H 2 O is water, H 2 O 2 is hydrogen peroxide peroxide

WHAT DO WE MEAN BY RADIOACTIVITY? SCIENCE PARK HS -- HONORS CHEMISTRY Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. There are numerous types of radioactive decay. The general idea: An unstable nucleus releases energy to become more stable

SOME KEY DEFINITIONS BEFORE WE MOVE ON Z = The Atomic Number. It’s the Number of Protons in the nucleus of an Atom. Nucleus: It’s where the Protons and Neutrons are located in an Atom. Protons: Positively Charged Particles in the Nucleus of the atom. Mass = (approx) 1 AMU Neutrons: Neutrally charged particles in the nucleus of an atom Mass = (approx) 1 AMU Mass Number of an atom: Number of Protons + Number of Neutrons in the nucleus of an atom. SCIENCE PARK HS -- HONORS CHEMISTRY

THREE COMMON TYPES OF RADIOACTIVE EMISSIONS SCIENCE PARK HS -- HONORS CHEMISTRY Alpha Beta Gamma

THREE COMMON TYPES OF RADIOACTIVE EMISSIONS - PENETRABILITY SCIENCE PARK HS -- HONORS CHEMISTRY Alpha particles may be completely stopped by a sheet of paper, beta particles by aluminum shielding. Gamma rays, however, can only be reduced by much more substantial obstacles, such as a very thick piece of lead.