Unit 2 - Atomic Bonding and Structure Flashcards

1
Q

4 properties of atoms

A
  1. Indivisible and indestructible
  2. All atoms of an element are identical
  3. Atoms of different elements have different weights and chemical properties
  4. A chemical reaction is a rearrangement of atoms
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2
Q

Primary Bonding

A

sharing or donating electron between atoms to form a more stable electron configuration

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3
Q

Secondary Bonding

A

Weak compared to primary bonds. They occur when there are dipoles in molecules

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4
Q

Sub-divisions of Primary Bonds

A
  1. Covalent - sharing electrons in saturated bonds
  2. Ionic - isolated ions only exist in gaseous form, the bonds exert forces in all directions
  3. Metallic - Electrons share orbitals with multiple atoms
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5
Q

Materials Characteristics for Covalent bonds (4)

A
For a solid;
V. High elastic Modulus
High inherent strength
High melting point
Low electrical conductivity
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6
Q

Material Characteristics for Ionic bonds (4, 3 examples)

A
High strength
High elastic modulus
High melting point
Poor electrical conductivity
Magnesia, Alumina and Cement
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7
Q

Material Characteristics for Metallic bonds

A
High melting points
high boiling points
Electrical conductivity
Opaqueness
Malleability
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8
Q

describe a ceramic and its bonding

A

inorganic non-metallic materials made from compounds of a metal and non-metal. the bonds are a mix of covalent and ionic

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9
Q

Material characteristics of ceramics

A

Electrical and thermal insulators

Brittle

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10
Q

What is an intramolecular force

A

the force which holds together the atoms making up the molecule or compound

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11
Q

what are the relationships between r, r0 and F between atoms

A

r > 10r0 there is a very little F (gas)
r < 10r0 Attractive forces increase
r < r0 Repulsive forces dominate
r=r0 F = dU/dr = 0

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12
Q

Seven properties that describe metals ceramics and polymers

A
  1. Hardness
  2. Resistance to corrosion
  3. Elastic Modulus
  4. Ductility
  5. Wear Resistance
  6. Conductivity
  7. Density
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13
Q

how many molecules per m^3 are there for solids. liquids and gases

A

10*28

1025

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14
Q

Elastic modulus of metals ceramics and polymers

A

Ceramics >200GPa
Metals 20-200GPa
Polymers <10GPa

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15
Q

Young Modulus

A
axial stiffness (shape volume)
easy to measure in a tensile test
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16
Q

what is shear modulus?

A
torsional stiffness (shape)
relatively easy to measure in a torsion test
17
Q

What is Bulk Modulus?

A
Volumetric stiffness (volume)
difficult to measure because of very small volume changes
18
Q

Young Modulus

A
axial stiffness (shape volume)
easy to measure in a tensile test`
19
Q

What is the quantity of the area under the a stress strain graph?

A

resilience