Atomic Structure and Electron Configuration

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Atomic Structure and Electron Configuration
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How would you define MATTER?

• MATTER is anything that has

MASS
VOLUME
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• All matter contain substances that are made of

ELEMENTS

• Simplest form of matter
• Cannot be broken down into simpler substances by
  CHEMICAL MEANS.

• Each element has its own characteristic set of
  physical and chemical properties used to identify
  it.

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What is the smallest unit of a chemical element
that has the properties of that element?

• ATOM

• Atoms can ONLY be broken down by bombarding the
  nucleus(nuclear process), but the elements
  properties will then be lost.

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Subatomic Particles

• The atom is made up of smaller particles with
  measurable properties such as

MASS and ELECTRICAL CHARGES
PROTON
0 NEUTRON 0
- ELECTRON -
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PROTON

• Positively charged particles

Located in the Nucleus
Define the element itself /its identity
Discovered by Ernest Rutherford
Made of even smaller particles called QUARKS
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0NEUTRON0

• Uncharged particles

Located in the Nucleus
Discovered by James Chadwick
Made of even smaller particles called QUARKS
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-ELECTRON-

• Negatively charged particles

Surround the atoms nucleus
Determine the properties of the atom chemical
reactions involve sharing or exchanging of these
e-
Discovered by J.J. Thomson
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NUCLEUS

• Central, dense part of the atom

Contains protons and neutrons0
Contains most of the atoms mass
Discovered by Ernest Rutherford
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Rutherfords model of the Atom

• The Planetary Model assumed that electrons were
  circling the nucleus like planets revolving
  around the sun.

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Rutherfords Model
electrons in orbits
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Modern Atomic Theory

• Neils Bohr, a Danish physicist, suggested that
• e- can be in only certain energy levels
• e- do not reside between levels, but rather
  jump from one to the other
• e- must gain energy to move to a higher energy
  level and vice-versa

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Modern Atomic Model

• the location of e- cannot be predicted precisely
• the electrons are represented as a cloud of
  varying density showing where an electron is more
  or less likely to be.
• orbital region in an atom with the highest
  probability of finding an e-

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Modern Electron Cloud Model
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Modern Electron Cloud Model

• The size of the electron clouds determine the
  size or volume of the atom.
• The atom is held together by the electric
  attractive force between the p and e- (positive
  and negative forces).

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Atomic Structure
Inner electron shell
Proton
Nucleus
Neutron
Outer electron shell
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Subatomic Particlesdistinguished by charge,
mass, location
a.m.u. atomic mass unit
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Periodic Table
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Atomic Number

• All atoms of the same element have the same
  number of protons ().
• The Atomic Number corresponds to the number of
  protons () in the nucleus.
• In a neutral atom of protons electrons

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Atomic Massalso called mass number

• Atomic Mass is the number of protons and neutrons
  in the nucleus

Atomic Mass p n0
18
8
8
18
Arsenic
75
33
75
Phosphorus
16
15
31
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ATOMIC STRUCTURE OF ELEMENT
Atomic mass
the number of protons in an atom
the number of protons and neutrons in an atom
Atomic number
the number of protons in an atom
number of electrons number of protons
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Isotopes are atoms of the same element having
different masses, due to varying numbers of
neutrons.
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Orbitals

• Think of orbitals as being like egg container
  that can only hold a certain amount of eggs.
• Electrons in these are always found in pairs(2
  e-)
• Orbitals are where the electrons are found in an
  atom.
• There are 4 different orbitals in which the
  electrons can be found
• S- Orbital orbital which holds up to 2 e- (1
  pair e-).
• P- Orbital orbital which holds up to 6 e- (3
  pair e-).
• D- Orbital orbital which holds up to 10 e- (5
  pair e-)
• F- Orbital orbital which holds up to 14 e- (7
  pair e-)

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Electron Configuration Table

• The orbits can hold only a specific number of
  electrons.
• Once an energy level is full, the electrons start
  filling the next level or period.

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Regular Periodic Table vs. Electron Orbital
Periodic Table
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Electron Configuration Table

• Electron Configuration is a code that describes
• how many electrons are in each energy level
• how they are arranged within each energy level
• Represented by 1s2
• A number ? represents energy level or period
• A lower case letter ? represents orbital
  sub-shell
• A number in superscript ? number of electrons

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Blocks and Sublevels

• We can use the periodic table to predict which
  sublevel is being filled by a particular element.

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ORDER OF FILLING
of e- 2 (n)2 n energy level or period
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Bohr Model Hydrogen
1s1

-
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Bohr Model Helium
1s2
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Bohr Model Lithium
1s2, 2s1
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Electrons exist in shells around the nucleus.
H 1 p (1 e-) He 2 p (2
e-) Li 3 p (3 e-) C 6 p
(6 e-) N 7 p (7 e-) O 8
p (8 e-)