models of atomic structure
DESCRIPTION
Models of Atomic Structure. Dalton Model. Unbreakable neutrally charged spheres. Thomson’s Cathode Ray Experiment. Cathode rays originate from neutrally charged atoms. . Cathod e Ray Tube. Cathode rays have a negative charge and are deflected by electrical charges and magnetic fields. - PowerPoint PPT PresentationTRANSCRIPT
Models of Atomic Structure
Dalton Model• Unbreakable neutrally
charged spheres.
Thomson’s Cathode Ray Experiment• Cathode rays originate
from neutrally charged atoms.
• Cathode rays have a negative charge and are deflected by electrical charges and magnetic fields.
• Cathode rays are electrons.
Cathode Ray Tube
Cathode Rays = Electrons
Cathode Rays = Electrons
Cathode Rays = Electrons
Plum Pudding Model• Negative electrons stuck
inside and on the surface of a positive pudding.
• Atom’s mass and positive charge is widely spread.
• Electrons might wander but mostly motionless unless kicked out by a lot of energy.
• Chocolate chips in ice cream.
Plum Pudding Model• Negative electrons stuck
inside and on the surface of a positive pudding.
• Atom’s mass and positive charge is widely spread.
• Electrons might wander but mostly motionless unless kicked out by a lot of energy.
• Chocolate chips in ice cream.
Rutherford’s Gold Foil Experiment – Predicted Results
Rutherford’s Gold Foil Experiment – Predicted Results
Rutherford’s Gold Foil Experiment – Actual Results
Actual Results
Rutherford’s Gold Foil Experiment• Most alpha particles
(42He) passed right
through the gold foil. • A few alpha particles
had very large deflections.
• The Plum Pudding model would predict only small deflections.
• The mass and positive charge of an atom is concentrated in a very small nucleus.
Rutherford-Bohr Model• Nucleus takes up very
little space. • Electrons jump up to a
higher energy level when they absorb energy.
• Electrons falls down to a lower energy level when they emit energy.
• Electrons orbit in regular “planet-like” energy levels around the positive nucleus.
Rutherford-Bohr Model• Nucleus takes up very
little space. • Electrons jump up to a
higher energy level when they absorb energy.
• Electrons fall down to a lower energy level when they emit energy.
• Electrons orbit in regular “planet-like” energy levels around the positive nucleus.
Quantum Model• Electron clouds not
orbits. • Electrons are not found
in fixed locations, but rather probabilities to be in a location.
s-orbitals
p-orbitals
Atomic ModelsAtomic Model Description
Dalton Solid, neutrally charged spheres.
Plum-Pudding Negatively charged electrons in a glob of positive charge. Like chocolate chips in vanilla ice cream.
Rutherford-Bohr
Negatively charged electrons orbit a positive nucleus. Like planets around the sun.
Quantum Electrons are in layers of clouds around the nucleus.
Key11NaSodium22.99
Atomic Number•Number of Protons•Number of Electrons (when atom is neutrally charged)
•Property unique to each element
Key
Average atomic mass*•Weighted Average number of Protons and Neutrons (approximately)
NaSodium22.99
11
Subatomic Particlesthe particles that make up an atom
• Protons – high mass, positive charge. Found in nucleus.
• Neutrons – high mass, no charge. Found in nucleus.
• Electrons – low mass, negative charge. Found orbiting around nucleus. (abbreviated e– )
Basic Electrical Charge Laws
+ and – : Attract(pull together)
– and – : Repel(push away)
+ and + : Repel(push away)
Like charges repel and Opposites attract
An Atom
Nucleus
1 proton = H = hydrogen
Why doesn’t the electron fall into the nucleus?• It orbits because the electron is moving really
fast around the nucleus. • Because the electron has such a low mass,
even a small amount of energy makes it move very fast.
An Atom
Nucleus
1 proton = H = hydrogen
Another AtomSize of atom
Size of nucleus
2 protons = He = helium
Cathode Rays = Electrons
NeFONCBBe
He
Li
H
Kr
ArCl
Br
XeI
SPSiMg Al
Ca
Na
K
4 e– in valence shell