Structure of an Structure of an AtomAtom

When you read the Periodic Table, When you read the Periodic Table, one of the most common questions one of the most common questions is, “Why do the names not match is, “Why do the names not match the symbol?” The reason is that the the symbol?” The reason is that the names names dodo match the symbol, but it is match the symbol, but it is the the LatinLatin name. name.

Example:Example: Silver – Silver – Symbol – AgSymbol – Ag Latin Name: ArgentumLatin Name: Argentum

Atomic ComponentsAtomic Components An element is matter that is composed of An element is matter that is composed of

one type of atom, which is the one type of atom, which is the smallestsmallest piece of matter that still retains the piece of matter that still retains the property of the element.property of the element.

The parts:The parts: Atoms are composed of particles called:Atoms are composed of particles called: Protons (+)Protons (+)

Neutrons (no charge)Neutrons (no charge)

Electrons (-)Electrons (-)

The Mass:The Mass:

Protons and Neutrons are found in a small, Protons and Neutrons are found in a small, positively charged (+) center of the atom called positively charged (+) center of the atom called the the nucleusnucleus that is surrounded by a cloud that is surrounded by a cloud containing electrons.containing electrons.

(If both protons and neutrons are found in the (If both protons and neutrons are found in the nucleus, why is it positive (+)?)nucleus, why is it positive (+)?)

DiagramDiagram

ProtonsProtons = positively charge 1+ = positively charge 1+

NeutronsNeutrons = do not have a charge (o) = do not have a charge (o)

ElectronsElectrons = negatively charge 1- = negatively charge 1- Atoms of different elements differ in the Atoms of different elements differ in the

number of number of protonsprotons they contain. they contain.

New Material - New Material - QuarksQuarks

Even Smaller – Even Smaller –

Protons and Neutrons are made up of smaller Protons and Neutrons are made up of smaller particles called particles called quarksquarks. Scientists have . Scientists have confirmed the existence of confirmed the existence of sixsix uniquely uniquely different quarks. Scientists theorize that the different quarks. Scientists theorize that the arrangement of three quarks held together with arrangement of three quarks held together with the strong nuclear force produces a proton. the strong nuclear force produces a proton. 3 3 more makes a neutron.more makes a neutron.

Quarks - Quarks -

QuarksQuarks To find quarks, scientists accelerate To find quarks, scientists accelerate

charged particles to tremendous speeds charged particles to tremendous speeds then force them to collide with other then force them to collide with other protons.protons.

ModelsModels Scientists use models to represent things Scientists use models to represent things

that are difficult to visualize, (that means that are difficult to visualize, (that means see in your mind)see in your mind)

AtomsAtoms Atoms are very small. It would take about Atoms are very small. It would take about

24,400 atoms staked on top of each other 24,400 atoms staked on top of each other to equal the thinness of a sheet of to equal the thinness of a sheet of aluminum foil.aluminum foil.

To study them, scientists developed To study them, scientists developed models that they can use to visualize how models that they can use to visualize how the atom is constructedthe atom is constructed

The Model has changed.The Model has changed. DemocritusDemocritus proposed the idea that proposed the idea that

atoms make up all substance in…atoms make up all substance in… 400 B.C.400 B.C.

But But AristotleAristotle disputed disputed DemocritusDemocritus’ ’ Theory saying that all matter is uniform Theory saying that all matter is uniform throughout and not composed of smaller throughout and not composed of smaller particles.particles.

Aristotle’s TheoryAristotle’s Theory AristotleAristotle’s Idea was accepted for over ’s Idea was accepted for over

2000 years.2000 years.

See what happens when you don’t study See what happens when you don’t study before you say things. They tend to be before you say things. They tend to be WRONG!!WRONG!!

Anyhow, he didn’t have the technology Anyhow, he didn’t have the technology that we have today either.that we have today either.

John DaltonJohn Dalton In the 1800’s In the 1800’s John DaltonJohn Dalton provided a provided a

model of the atom as a solid sphere.model of the atom as a solid sphere.

But over time and experiments, scientists But over time and experiments, scientists have modified the atomic model. The have modified the atomic model. The model that we use today is the model that we use today is the accumulated knowledge of almost 200 accumulated knowledge of almost 200 years.years.

Thompson’ s ModelThompson’ s Model The chocolate chip cookie modelThe chocolate chip cookie model

What’s missing?What’s missing?

Rutherford’s AtomRutherford’s Atom What’s missing?What’s missing?

Bohr ModelBohr Model Diagram like planet’s orbitals.Diagram like planet’s orbitals.

D

Electron CloudElectron Cloud Newest ModelNewest Model

Electron CloudElectron Cloud Developed in 1926, the Developed in 1926, the electron cloudelectron cloud is is

the area around the nucleus of an atom the area around the nucleus of an atom where its electrons are most likely found. where its electrons are most likely found.

The electron cloud is The electron cloud is 100,000100,000 times times larger than the diameter of the nucleus, larger than the diameter of the nucleus, but an electron is much smaller than a but an electron is much smaller than a protonproton

The atom’s mass:The atom’s mass: Proton = 2000 times larger than an electron.Proton = 2000 times larger than an electron.

Electrons = the electron cloud makes up an Electrons = the electron cloud makes up an atom’s volume. (space) Electrons are very tiny.atom’s volume. (space) Electrons are very tiny.

Why we don’t see them.Why we don’t see them. Because an electron’s mass is small and Because an electron’s mass is small and

the electron is moving so quickly around the electron is moving so quickly around the nucleus, it is impossible to describe the nucleus, it is impossible to describe its exact location in the atom.its exact location in the atom.

What do electrons do?What do electrons do? Each electron travels at an average distance Each electron travels at an average distance

form the nucleus, depending on its energy. form the nucleus, depending on its energy.

These average distances are referred to as These average distances are referred to as energy levels.energy levels.

Energy levels are areas of the cloud where the Energy levels are areas of the cloud where the electrons are more likely to be found.electrons are more likely to be found.

Energy LevelsEnergy Levels