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MIME 260 > 2. Atomic Bonds > Flashcards

2. Atomic Bonds Flashcards

1
Q

FLOWCHART: Sub-atomic structure defines _____, which defines ____ and ____.

A

Atomic bonds, which defines basic mat properties as well as material types.

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2
Q

Atomic packing is modified by ____

A

Packing defects

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3
Q

What two things define microstructure?

A

Atomic packing and packing defects.

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4
Q

Materials Processing techniques controls what two things?

A

Packing defects and macroscopic defects

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5
Q

What gives “actual material properties”

A

atomic packing and packing defects, modded by macroscopic defects.

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6
Q

What defines ideal material properties?

A

Microstructure does.

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7
Q

What are two ways to control atomic defects and macroscopic defects?

A

Materials processing techniques, as well as component production techniques (i.e. machining can improve surface finish)

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8
Q

What are the ICME scales?

name five

A 
Electronic
Nano 
Micro (microstructure)
Meso (microstructure)
Macro
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9
Q

BONDING

What is a material?

A

A group of atoms, bonded together, used as a material

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10
Q

Why do atoms group together?

A

Atoms group together to minimize energy.

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11
Q

What is the ground state?

A

The lowest energy state of ONE atom

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12
Q

When is ground state achieved?

A

when the outermost shell is filled

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13
Q

What is a stable electron configuration?

A

Outermost shells are filled. i.e. noble gases.

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14
Q

What do you call an atom with a slight excess of electrons?

A

Metallic or electropositive.

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15
Q

What do you call an atom with a slight deficiency of electrons

A

Nonmetallic or electronegative.

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16
Q

Compare and contrast ground state and stable electron configuration.

A

They both describe the lowest energy state. Ground state is for ONE atom, S.E.C. is for a GROUP of atoms.

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17
Q

How does the ground state and stable electron configuration differ for noble gases

A

for noble gases they are the same.

18
Q

HOW DO ATOMS BOND

A

By coulombic forces

19
Q

What are coulombic forces?

A

Forces created between charged particles: repulsive if they’re charged the same way

20
Q

How are these coulombic forces created?

A

By creating a stable electron configuration

21
Q

How does ionic bonding happen?

A

Metal gives an electron to the non-metal. Coulombic forces keep the two ions attracted.

22
Q

Is ionic bonding directional?

A

No - forces are always attractive

23
Q

Metals, polymers, ceramics: which one performs ionic bonding?

A

Ceramics!

24
Q

Up/down and left/right: which directions increase electronegativity?

A

UP, RIGHT increasing EN.

Electropositive: excess of electrons

25
Q

RANDOM FACT

A

Ionic bonding creates compounds (i.e. ceramics)

26
Q

Why do Ca or K not bond ionically?

A

Well, neither Ca or K can gain electrons. They can only give.

27
Q

When does ionic bonding occur?

A

When electronegativities are far apart.

28
Q

COVALENT BONDS SECTION

A

Yay!

29
Q

When does covalent bonding happen?

A

Between super electronegative atoms.

30
Q

What elements are considered non-metallic?

A

The noble gases, fluorides, H, and NOPS.

31
Q

What elements are considered intermediate?

A

(think of semiconductors.

B, C, Si, Ge, As, Se, Te

32
Q

How do covalent bonds work?

A

At the point of shared electrons, there is an electron “cloud” that attracts the two nuclei.

33
Q

Are covalent bonds directional?

A

Yes, they are.

34
Q

Can a material have a mix of ionic and covalent bonds?

A

Yes! It’s termed “ionic character”. Increasing differences in electronegativity results in increasing ionic character, and thus an increase in ionic bonding. There are equations.

35
Q

METALLIC BONDINGS

A

Yay!

36
Q

Why does metallic bonding happen?

A

The atoms involved in metallic bonding are too polite - they readily give up all their electrons. Leads to a sea of delocalized electrons moving amongst metal ions.

37
Q

What are secondary or van der vaals bonds?

A

If the electrons and protons are separated, dipoles form. These attract other dipoles

38
Q

When are van der waals bonds important?

A

they’re important when not obscured by a strong primary bond (i.e. ionic or metallic).

39
Q

What can van der waals bonds determine?

A

Things like the solidification point of gases.

40
Q

Van der waals are important for plastics!

A

Yeah! Plastics are weakish because of these van der waals forces

41
Q

How do dipoles form?

A

1) Moving electrons

Can condense inert gases!

42
Q

Why does liquefaction occur at certain temperatures?

A

Because it just so happens to be the arrangement of lowest energy.

MIME 260 (9 decks)

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