atomic structure powerpoint presentation by computer careers
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Powerpoint Presentation on Atomic Structure by Computer Careers.What is an Atom?ATOMIC STRUCTURE,There are two ways to represent the atomic structure of n element or compound,DOT & CROSS DIAGRAMS and many more ....TRANSCRIPT
CHEMISTRY PROJECTB
YCOMPUTE
R CAREERS
ATOMIC STRUCTURE
What is an Atom?
• Matter is anything that takes up space and has mass.
• All matter is made of atoms
• Atoms are the building blocks of matter, sort of how bricks are the building blocks of houses.
Parts of Atom• An atom has three parts:
• Proton = positive
• Neutron = no charge
• Electron = negative
• The proton & neutron are found in the center of the atom, a place called the nucleus.
• The electrons orbit the nucleus.
ATOMIC STRUCTUREATOMIC STRUCTURE
Electrons are arranged in Energy Levels
or Shells around the nucleus of an atom.
• first shell a maximum of 2 electrons
• second shell a maximum of 8
electrons
• third shell a maximum of 8
electrons
ATOMIC STRUCTUREATOMIC STRUCTURE
There are two ways to represent the atomic
structure of n element or compound;
1. Electronic Configuration
2. Dot & Cross Diagrams
ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATION
With electronic configuration elements are
represented numerically by the number of
electrons in their shells and number of shells.
For example;
NNitrogen
14
2 in 1st shell
5 in 2nd shell
configuration = 2 , 5
2 + 5 = 7 7
DOT & CROSS DIAGRAMSDOT & CROSS DIAGRAMSWith Dot & Cross diagrams elements and
compounds are represented by Dots or
Crosses to show electrons, and circles to
show the shells. For example;
Nitrogen N XX X
X
XX
X N7
14
1910
Ernest Rutherford
oversaw Geiger and Marsden carrying
out his famous experiment.
they fired Helium nuclei at a piece of
gold foil which was only a few atoms
thick.
they found that although most of
them passed through. About 1 in
10,000 hit
Rutherford’s InventionRutherford’s Inventiongold foil
helium nuclei
They found that while most of the helium nuclei
passed through the foil, a small number were
deflected and, to their surprise, some helium
nuclei bounced straight back.
helium nuclei
Rutherford’s new evidence allowed him
to propose a more detailed model with a
central nucleus.
He suggested that the positive charge
was all in a central nucleus. With this
holding the electrons in place by
electrical attraction
However, this was not the end of the story.
ARISEN OF NEILS BOHRARISEN OF NEILS BOHR
1913
Niels Bohr
studied under Rutherford at the Victoria
University in Manchester.
Bohr refined Rutherford's idea by
adding that the electrons were in
orbits. Rather like planets orbiting the
sun. With each orbit only able to
contain a set number of electrons.
Rutherford’s alpha scattering experiment
source of
alpha particles
Thin gold foil
Photographic film
Beam of particles most
pass straight
through
1 in 20 000 deflected
Rutherford’s explanation
atoms of gold
in gold foil
Path of an particle
nucleus of
gold atom
All these particles pass straight through the empty space that makes up most of the atom.
This particle
passes close enough to nucleus to be repelled
As particles are positively charged, the nucleus must contain positively
charged protons.
atoms of gold
in gold foil
nucleus of
gold atom
As only 1 in every 20 000 particles are repelled the nucleus must be very small.
Size of the nucleus
Rutherford’s model of the atom
Tiny nucleus containing the positively charged protons.
Rest of atom is mostly empty space. The negatively charged
electrons are spinning round the nucleus.
Section 3.1
The Limitations of Rutherford’s Atomic Model
Chapter 3: Atomic Models and Properties of Atoms
• radiation must be emitted, so it was expected that a continuous spectrum of light energy was being given off
• because of radiation, the electron would lose energy and its orbit would decrease until it spiraled into the nucleus, destroying the atom
Bohr Model of Atom• The Bohr Model shows
all of the particles in the atom.
• In the center is circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N.
• In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e.
++++
--
--
Bohr’s Atomelectrons in orbits
nucleus
Bohr's Model of the Atom
Bohr's model:-electrons orbit the nucleus like planets orbit the sun
-each orbit can hold a specific maximum number of electrons
-electrons fill orbits closest to the nucleus first.
Bohr's Model of the Atom
Niels Bohr (1913):-studied the light produced when atoms were excited by heat or electricity
Rutherford's model couldn't explain why unique colours were obtained by atoms of different elements
Bohr proposed that electrons are in orbits & when excited jump to a higher orbit. When they fall back to the original they give off light
Bohr's Model of the Atom
e.g. fluorine:#P =
#e- =
#N =
9
9
109P
10N
Today’s quantum mechanical model of the atom incorporates the wave properties of electrons.
Section 3.2
The Quantum Mechanical Model of the Atom
An electron density diagram represents an atomic orbital.
Chapter 3: Atomic Models and Properties of Atoms
Wave functions, initially described by Erwin Schrodinger, represent a region in space around a nucleus where an electron will be found. This region of space is called an atomic orbital
Section 3.2
The Quantum Mechanical Model of the Atom
The circle does not represent a real boundary.
Chapter 3: Atomic Models and Properties of Atoms
Atomic orbitals can be visualized as “fuzzy clouds”
• The higher the density of the “cloud,” the higher the probability of finding an electron at that point.
• The cloud has no definite boundary.• The region where an electron will spend 90
percent of its time is depicted by drawing a circle.
Section 3.1
Quantum Numbers Describe Orbitals
Chapter 3: Atomic Models and Properties of Atoms
Electrons in the quantum mechanical model of the atom are described using quantum numbers.Three quantum numbers describe the distribution of electrons in the atom and a fourth describes the behaviour of each electron.
Symbols for the four quantum numbers:
n l ml ms
Section 3.2
The Principle Quantum Number, n
Chapter 3: Atomic Models and Properties of Atoms
• Is the first quantum number• Describes the energy level, or shell, of an
orbital• All orbitals with the same n value are in the
same shell• The larger the n value, the larger the size of the
shell• Values can range from n = 1 to n = ∞
n = 1 first shelln = 2 second shelln = 3 third shelln = 4 fourth shell
Section 3.2
The Orbital-Shape Quantum Number, l
Chapter 3: Atomic Models and Properties of Atoms
• Is the second quantum number• Describes the shape of an orbital• Refers to energy sublevels, or subshells• Values depend on the value of n. They are positive
integers from 0 to (n – 1)• Each value is identified by a letter
l = 0 orbital sl = 1 orbital pl = 2 orbital dl = 3 orbital f
An energy sublevel is identified by combining n with the orbital letter. For example, n = 2, l = 1: 2p sublevel
Section 3.2
The Magnetic Quantum Number, ml
s, p, and d orbitals have characteristic shapes.
Chapter 3: Atomic Models and Properties of Atoms
• Is the third quantum number • Indicates the orientation of the orbital in space• For a given l there are (2l +1) values for ml• The total number of orbitals for an energy level
is n2
NucleusNucleus
11stst shell shell
22ndnd shell shell
33rdrd shell shell