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chem > Bonding > Flashcards

Bonding Flashcards

1
Q

give the definition of metallic bonding

A

its the strong electrostatic attraction between positive metal ions and sea of delocalised electrons

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2
Q

how do you draw metallic bonding diagrams

A

always draw 6 atoms, work out charge of ion and draw correct number of electrons (sum of all charges)

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3
Q

how do you compare the strength of metallic bonds

A

Ions have stronger metallic bonding if;
- they have higher charge
- if they are the smaller metal ion
- if they have more delocalised electrons
Finally state that there’s a stronger electrostatic attraction between positive metal ions and delocalised electrons

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4
Q

why is the bonding in magnesium stronger than in sodium

A

Mg2+ has higher charge than Na+
Mg2+ is a smaller ion than Na+
Mg2+ has more delocalised electrons than Na+
Therefore Mg2+ has stronger electrostatic attractions between positive metal ions and delocalised electrons

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5
Q

Give the properties of metals

A

-Good electrical and thermal conductors
-They are strong
-They are malleable and ductile
-Have high melting/boiling points

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6
Q

How are metals good conductors of heat and electricity

A
  • they are good conductors of heat because delocalised electrons help transfer energy through the metal very efficiently
    -the electrons are delocalised as they can flow and carry charge so can conduct electricity
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7
Q

How are metals strong and why do they have high Mp and Bp’s

A
  • they have strong electrostatic attractions between positive metal ion and delocalised electrons so stronger the strength of metallic bond, the higher the Mp and Bp
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8
Q

what is the definition for covalent bonding

A

shared pair of electrons between 2 atoms

the shared electrons hold together because the attraction forces are stronger than repulsion forces

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9
Q

what are macromolecular structures

A

carbon, silicon and silicon dioxide

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10
Q

why do macromolecular structures have high Mp and Bps

A

because they have many strong covalent bonds which require lots of energy to be broken

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11
Q

what are allotropes

A

they are different structural forms of the same element

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12
Q

what are the properties of diamond

A

-each carbon makes 4 covalent bonds so its got a high Mp and Bp because lots of the covalent bonds need lots of energy to be broken
-doesn’t conduct electricity as it has no free/delocalised electrons

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13
Q

what are the properties of graphite

A

-each carbon akes 3 covalent bonds and one outer electron becomes delocalised so graphite can conduct electricity as delocalised electrons can move
-layers of carbon which makes it soft
-between layers are weak intermolecular forces

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14
Q

what are simple molecular structures made up of

A

molecules

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15
Q

what are the properties of a simple molecular structure

A
  • has strong covalent bonds between atoms and weak intermolecular forces between molecules
  • have low melting and boiling points because intermolecular forces are weak so require little energy to be broken
  • don’t conduct electricity because there’s no delocalised electrons
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16
Q

what is the structure for ionic bonding

A

giant ionic lattice

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17
Q

definition of ionic bonding

A

an ionic bond is the strong electrostatic attractions between oppositely charged ions (metals and non-metals)

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18
Q

give the properties of ionic compounds

A
  • high boiling and melting points because they have strong electrostatic attractions which need lots of energy to break them
  • they can conduct electricity when molten or aqueous as ions are free to move and carry current
    -ionic compounds tend to be brittle and shatter easily
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19
Q

formula for ammonium ion

A

NH4+

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20
Q

formula for hydroxide ion

A

OH-

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21
Q

formula for nitrate ion

A

NO3-

22
Q

formula for nitrite ion

A

NO2-

23
Q

formula for hydrogencarbonate ion

A

HCO3-

24
Q

formula for chlorate (I) ion

A

ClO-

25
Q

formula for chlorate (v) ion

A

ClO3-

26
Q

formula for carbonate ion

A

CO3 2-

27
Q

formula for sulfate ion

A

SO4 2-

28
Q

formula for sulfite ion

A

So3 2-

29
Q

formula for dichromate ion

A

Cr2O7 2-

30
Q

phosphate ion formula

A

PO4 3-

31
Q

what is a coordinate bond and what are the conditions to create one

A
  • a shared pair of electrons between 2 atoms when both electrons come from same atom
  • for this you need one atom with lone pair of electrons and one atom with space for 2e- so it can accept them
32
Q

explain the formation of the coordinate bond in NH4+

A

The lone pair of electrons on N from NH3 is donated to the H+

33
Q

what does valence mean

A

the outer shell of electrons ( the electrons used in bonding)

34
Q

what is the strength of repulsion of electrons

A

bondpair- bondpair repulsion is less than bondpair - lonepair repulsion which is less that lonepair- lonepair repulsion

35
Q

what is electronegativity

A

the power of an atom to attract the pair of electrons in a covalent bond

36
Q

which factors determine how electronegative an element is

A
  • nuclear charge
  • size of atom
  • shielding
37
Q

why does the electronegativity increase across a period

A

increases because
- they all have same number of shells so similar shielding
- so numbers of protons increase
- atomic radius increases so
- there’s a strong attraction between nucleus and pair of electrons in a covalent

38
Q

why does C - H not have a partial charge

A

because it has too similar electronegativity

39
Q

what does a non - polar molecule consist of

A
  • atoms bonded have same electronegativity
  • symmetrical distribution of electrons / charge
  • dipoles cancel out
    (eg. Cl-Cl)
40
Q

what does a polar molecule consist of

A
  • differences in electronegativity is shown by a partial charge
  • delta - is given to the more electronegative atom
  • delta + is given to the less electronegative atom
  • unsymmetrical distribution of electrons leads to a polar molecule
    (eg. H-Cl)
41
Q

how do you determine is a molecule has hydrogen bonding

A
  • if it has a lone pair and the following bonds
    O - H
    N - H
    F - H
42
Q

how do you determine if a molecule has permanent dipole - dipoles

A

it will be a polar molecule (unsymmetrical)

43
Q

how do you determine if a molecule has induced dipole dipoles ONLY

A

it will be a non- polar molecule (symmetrical)

44
Q

how does hydrogen bonding arise

A
  • large difference in electronegativity between O , N , F when bonded to H
  • H therefore gets a very strong delta + charge
  • lone pair of electrons on another molecule is attracted to delta + H.
45
Q

how do you draw Hydrogen bonding in water

A

straight line between O - H - lone pair - O - H

46
Q

how does permanent dipole - dipole forces arise

A
  • in polar molecules
  • permanent partial charges ( delta + , -) cause a dipole across the molecule
  • delta + on one molecule is attracted to delta -on another molecule
47
Q

how does a Van der Waals forces arise

A
  • present in all molecules, but is only force in non-polar molecules
  • random movement of electrons creates an uneven distribution of electrons and creates a temporary dipole dipole
  • this will then induce a dipole on neighbouring molecules
  • dipoles attract
48
Q

what affects the strength of a van der vaals force

A
  • size of molecule , larger the molecule stronger the van der vaals force
  • molecular mass (Mr) higher the Mr stronger the VDW force
  • surface are contact between carbon chains, longer the carbon chain the stronger the VDW force
49
Q

describe hydrogen bonding in ice, proteins and DNA

A
  • ice is less dense than water because the hydrogen bonds in ice hold the molecules further apart so there’s more gaps and spaces between molecules
  • proteins are held in 3D complex sha[es by hydrogen bonds between N-H groups and C=0 groups
  • hydrogen bonding between DNA bases A-T C-G
50
Q

why does argon have the lowest mp

A

its a single atom that’s difficult to polarise

chem (9 decks)

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