Structure of an Atom part 2

Atomic Theory

Theory where matter is composed of atoms.

Solid Sphere Model

Made by John Dalton, he suggested that all matter is made up of atoms, which are indivisible and indestructible

● Recognized that the different

atoms of a particular element

are different from other

elements.

Chemical Reactions

According to Daltons atomic theory, this involves an arrangement of atoms to form products

cant explain isotopes, nothing about the structure was properly explained, people later found out that atoms are divisible

Demerits of Daltons theory

Plum pudding model

● Recognized electrons as

components of atoms.

● Imagined as a positively charged

cloud with a bunch of electrons

around it.

J.J Thompson

Plum pudding model?

Nuclear Model

Has realized that the positive

charge was localized within the

nucleus of an atom.

Heinsenberg’s uncertainty principle

stated that no two conjugate physical quantities could be measured simultaneously with 100% accuracy

Stark effect

Phenomenon of deflection of electrons in the presence of a electric field

Earnest Rutherford

Nuclear Model?

Planetary Model

Proposed stable electron orbits;

explained the emission spectra

of some elements.

● Electrons are quantified; they

have a fixed energy.

Niels Bohr

Planetary Model?

Magnetic quantum number

● Symbol: ml

● Values: -l, ..., 0, ..., +l

● Specifies the orbitals and

indicates the orientation.

Quantum model

Shows electrons don’t move

around the nucleus in orbits,

but in clouds where their

position is uncertain.

● It is impossible to know the

exact location of the electron.

Aufbau’s principle

the filling of electrons should take place in accordance with the ascending order and energy of orbitals

Pauli’s exclusion principle

no two electrons can have four quantum numbers to be the same, r if two electrons have to be placed in an energy state, they should be placed with opposite spies

Hunds Rule

States that electrons in the orbital

are filled up by + spin first. Upward spin first

1/2

before downward spin.

Erwin Schrodinger

Quantum model?

Electrons

An atom is composed of a nucleus surrounded by

Ions

- An atom with a net electric charge with the loss

or gain of an electron.

Cation

atoms with a positive charge

Anions

atoms with a negative charge

Isotopes

has the same atomic number but can differ with the number of neutrons

Quantum Numbers

Used to get the electron configuration and the

probable location of e

Principle

● Symbol: n

● Values: 1, 2, 3, ...

● Specifies the main energy level

and indicates the size.

Azimuthal

● Symbol: l

● Values: 0, 1, 2, 3, ..., n - 1

● Specifies the sub-level and

indicates the shape.

Spin

● Symbol: ms

● Values: +1/2, -1/2

● Specifies the spin state and

indicates the spin.

Shell

Same with the number of its principles

(n).

Subshell

Same with the number of principle (n)

and azimuthal (l).

Orbital

Same with the number of principle (n),

azimuthal (l), and magnetic (m).

Allotropes

Pure carbon exists in different forms called ?,

with different arrangements of the atoms depending on the temperature and pressure.

Diamond

● 4 carbon atoms share a

Covalent bonding.

> Each carbon atom shares

each one of its valence

electrons with an adjacent

carbon, therefore each carbon

atom has a full outermost

quantum shell.

● 3550°C melting point.

> Because of the strong

covalent bonding between

atoms.

● One of the highest thermal

conductivities.

> Because of the rigidity of its

covalently bonded structure.

● An electric insulator

> There is no room for

electrons to conduct electricity

between the sharing of the

valence electrons and its

neighboring carbon atoms.

● Also one of the hardest

substances known, which

makes it often used in cutting

tools.

Nanoscience

Study of materials at the

nanometer length scale

Graphite

● Contains only carbon atoms.

● Atoms are arranged in layers.

● Each layer of carbons is

arranged in a hexagonal

pattern.

● 3 carbon atoms share Covalent

bonding.

> 4th bond is between the

layers, but much weaker than

van der Waals bond.

● Also has a high melting point

● Each carbon atom has three

strong bonds in the layer.

● Lower density because of the

layer structure.

> Atoms are not as packed

closely together

● Electrically conductive.

> This is because of the fourth

electron of each carbon atom,

which is not covalently bonded

in the plane.

Buckminsterfullerene

“Buckyballs”

● Discovered in 1985.

● A two-dimensional pattern of

12 regular pentagons and 20

regular hexagons.

● Forms like a soccer ball.

● Has 60 corners.

● Can enclose other atoms

within them, strong, and

interesting magnetic and

conductive properties.

Carbon nanotubes

● Sheets of graphite rolled into

tubes with hemispherical

fullerene caps on the end.

● A single sheet of graphite, or

called as graphene, can be

rolled in different directions to

create nanotubes with

different configurations.

- Considered as possible

conductors of electricity in

advanced nanoelectronic

devices.

● Can be single-walled or

multi-walled.

● Multi-walled nanotubes consist

of multiple concentric

nanotubes.

● Typically 1-25 nm in diameter

and are on the order of

microns long.

● Carbon nanotubes with

different configurations

display different material

properties.

● Electrical properties of the

nanotubes depend on the

helicity and diameter of the

nanotubes.

● These are currently used as

reinforcement to strengthen

polymers and as tips for

atomic force microscopes.

● Considered as possible

conductors of electricity in

advanced nanoelectronic

devices.

Amorphous materials

• Short-range atomic

arrangements

Crystalline materials

Short- and long-range

atomic arrangements.

❖ The long-range atomic order

is in the form of atoms or

ions arranged in a

three-dimensional pattern

which repeats over much

larger distances (from 10

nm to cm).

Nanotechnology

The manipulation and

development of devices at the

nanometer length scale.

Nanostructure

Structure of a material at a

length scale of 1 to 100 nm.

Microstructure

● The structure of materials at a

length scale of 100 to 100,000

nm or 0.1 to 100 micrometers.

● The microstructure typically

refers to features such as the

grain size of a crystalline

material.

Macrostructure

The structure of a material at a

macroscopic level where the

length scale is >100 um

(microns).

● Features that constitute

macrostructure include porosity,

surface coatings, and internal

and external microcracks.