starter s-23 what are the 3 parts of an atom?. atomic structure chapter 4
TRANSCRIPT
Starter S-23
What are the 3 parts of an atom?
Atomic Structure
Chapter 4
4.1 Defining the Atom
Chapter 4
4.1 Defining the AtomEarly Model
1. Democritus (460-370 B.C.) – matter consists of tiny indivisible, unchangeable particles
2. first to coin term atom
3. Did not use scientific method
4.1 Defining the AtomDalton’s Atomic Theory
Dalton (1766-1844) – used scientific method to support Democritus’s ideas
Most famous for work with the atom, but also worked with
a.Weather
b.Color blindness
4.1 Defining the AtomPostulates of Dalton’s Atomic Theory
1. Elements are composed of tiny indivisible particles called atoms
2. Atoms of the same element are the same, they are different from atoms of any other element
3. Atoms combine in simple whole number ratios to form compounds
4. Chemical reactions join, separate, or recombine atoms, the atoms never change
4.1 Defining the AtomAtoms are very small
Can only be observed with a scanning tunneling microscope
Size is 1 x 10-10m
Or 0.0000000001 m
4.2 Structure of the Nuclear Atom
Chapter 4
4.2 Structure of the Nuclear Atom
Three kinds of sub atomic particles
Proton, Neutron, Electron
Actually many more
Name ofLepton
SymbolMass(MeV)
Electron e 0.511
Electron Neutrino e ~ 0
Muon 106
Muon Neutrino ~ 0
Tau 1,777
Tau Neutrino ~ 0
4.2 Structure of the Nuclear AtomThree kinds of sub
atomic particlesProton, Neutron,
ElectronActually many moreFermions
LeptonsQuarks
HadronsBaryonsMeson
Bosons
Name ofLepton
SymbolMass(MeV)
Electron e 0.511
Electron Neutrino e ~ 0
Muon 106
Muon Neutrino ~ 0
Tau 1,777
Tau Neutrino ~ 0
4.2 Structure of the Nuclear Atom
Electron
Discovered by JJ Thompson (1897)
Negative charge
Very small mass (we will call it 0)
Discovered using a cathode ray tube
Deflects toward the positive plate, so stream of negative particles
Cathode Ray
Simulation
4.2 Structure of the Nuclear Atom
Robert Millikan – preformed experiments to calculate the amount of negative charge
4.2 Structure of the Nuclear Atom
Proton
Positive Charge
Relative Mass of 1 (1840 x electron)
Found in Nucleus
Discovered in 1886 by Eugen Goldstein
Starter S-24
What did each of these scientists contribute to our understanding of the atom?
A. Democritus
B. JJ Thompson
C. Robert Millikan
D. James Dalton
4.2 Structure of the Nuclear Atom
Neutron
Neutral
Found in nucleus
Relative mass is 1
Discovered in 1932 by James Chadwick
4.2 Structure of the Nuclear Atom
In SummaryParticle Symbol Relative
ChargeRelative Mass
Actual Mass
Electron e- 1- 1/1840 (0)
9.11x10-28
Proton p+ 1+ 1 1.67x10-24
Neutron n0 0 1 1.67x10-24
4.2 Structure of the Nuclear Atom
In SummaryParticle Symbol Relative
ChargeRelative Mass
Actual Mass
Electron e- 1- 1/1840 (0)
9.11x10-28
Proton p+ 1+ 1 1.67x10-24
Neutron n0 0 1 1.67x10-24
4.2 Structure of the Nuclear Atom
The Nucleus
Originally believed that all the particles were spread out evenly
1911 Rutherford’s Gold Foil Experiment proved that matter is mostly empty space with a dense positive nucleus
Gold Foil Experiment
Scattering
4.2 Structure of the Nuclear Atom
The Rutherford Model of the Atom
1. The atom is mostly empty space
2. All the positive charge and most of the mass is concentrated in a small nucleus
3. Protons and neutrons are in the nucleus
Called the Nuclear Atom
Does not explain electrons
4.3 Distinguishing Among Atoms
Chapter 4
4.3 Distinguishing Among Atoms
Protons – determine what element is the atom is
Hydrogen – 1 proton
Still Hydrogen if you add
1 Neutron
2 Neutron
4.3 Distinguishing Among Atoms
However, if we add a proton
The element is now Helium
4.3 Distinguishing Among Atoms
Atomic number – the number of protons in an element
This is called the value of Z
A is the mass number
X is the symbol
Hydrogen would beAZ X
4.3 Distinguishing Among Atoms
Atomic number – the number of protons in an element
This is called the value of Z
A is the mass number
X is the symbol
Hydrogen would be11H
4.3 Distinguishing Among Atoms
Atomic number – the number of protons in an element
This is called the value of Z
A is the mass number
X is the symbol
Helium would be11H
4.3 Distinguishing Among Atoms
Atomic number – the number of protons in an element
This is called the value of Z
A is the mass number
X is the symbol
Helium would be42He
4.3 Distinguishing Among Atoms
In a uncharged (neutral) atom, the number of protons equals the number of electrons
If extra electrons are added
Atom becomes negative42He
4.3 Distinguishing Among Atoms
In a uncharged (neutral) atom, the number of protons equals the number of electrons
If extra electrons are added
Atom becomes negative42He
4.3 Distinguishing Among Atoms
In a uncharged (neutral) atom, the number of protons equals the number of electrons
If extra electrons are added
Atom becomes negative
If electrons are lost
Atom becomes positive
42He
4.3 Distinguishing Among Atoms
In a uncharged (neutral) atom, the number of protons equals the number of electrons
If extra electrons are added
Atom becomes negative
If electrons are lost
Atom becomes positive
42He
Starter S-25
How many protons and electrons are in the following atom?
2178
O
4.3 Distinguishing Among Atoms
Mass Number (A) is the total number of protons and neutrons
So hydrogen with no neutrons
With one neutron
11H21H
4.3 Distinguishing Among Atoms
So the number of neutrons is
Neutrons = A – Z
Isotope – same element, but different numbers of neutrons, and different mass numbers
4.3 Distinguishing Among Atoms
4.3 Distinguishing Among Atoms
There are two isotopes of Carbon.
One has a mass of 12, and the other a mass of 13.
What is the symbol for Carbon-12?
How many neutrons
N = A – Z
N = 12 – 6 = 6126C
4.3 Distinguishing Among Atoms
Atomic Mass
Determined using a mass spectrometer
Masses are given relative to the mass Carbon-12
1 amu (Atomic Mass Unit) = 1/12 the mass of 126C
Mass Spectrometer
4.3 Distinguishing Among Atoms
The atomic mass is a weighted average of the mass of different isotopes
Depends on the mass of the isotopes and how common they are
Carbon-12 mass = 12.000, abundance is 98.89%
Carbon-13 mass = 13.003, abundance is 1.11%
011.12144333.08668.11
1443333.00111.0003.13
8668.119889.0000.12
x
x
4.3 Distinguishing Among Atoms
Your turn
Chlorine-35, mass=34.969, abundcance=75.77%
Chlorine-37, mass=36.966, abundance=24.23%
45.359569.8496.26
9569.82423.0966.36
496.267577.0969.34
x
x
4.3 Distinguishing Among Atoms
The Periodic Table
Arranged by increasing atomic number
Columns by similar chemical properties
Periodic Table
4.3 Distinguishing Among Atoms
Period – horizontal row
Group (family) – vertical row
Periodic – chemical properties repeat