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bonding Flashcards

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1
Q

what is structure of ions

A

A regular lattice of alternating positive and negative ions

lattice held by electrostatic forces

Crystal structure

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2
Q

properties of lattice and why (5)

A

very high melting point due to strong electrostatic attraction between oppositely charged ions therefore requires a lot of energyy to break

Generally soluble in H2O- as water is very polar so it can disrupt the electroctatic attractions between the ions and break them up

insulator when solid- ions are fixed in position so cannot carry a charge

Electrical conductors when molten/ dissolved- as ions are free to move so able to carry a charge

Brittle - when moved. Ions no longer have an alternating arrangement which means they repel each other and the lattice breaks

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3
Q

what is a covalent bond

A

shared pair of elctrons with opposite spins, and one electron is donated by each atom

(multiple eg double bond when 2 pairs of e- shared etc)

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4
Q

what does a covalent bind form between

A

forms between elements that have high electronegativty values (non-metals)

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5
Q

what forces are involved in a covalent bond

A

highly negative/ high e- density where elctrons shared

And the very strong attraction between the electrons and positive nuclei

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6
Q

types of covalent structures

A

molecular:

simple covalent i.e CH4, H2O

macromolecular:

giant covalent i.e. diamond and graphite

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7
Q

what is a coordinate bond (dative)

A

a covalent bond formed when both electrons are donated by the same atom

once formed, acts in the same way as a covalent bond

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8
Q

how is ice formed

A

H2O is a covalent bonded molecule therefore hydrogen bonding exists between molecules

between 0ºC - 100ºC, bonds hold molecules close to each other but allow free movement

Below 0ºC, molecules have less energy so hydrogen bonding fix molecules in position

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9
Q

what structure does ice have

A

Ice has 3d hexagonal crystal structure

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10
Q

how are properties of ice affected by structure (2)

A

ice floats: spaces creates b/c of 3D hexagonal crystal structure

spaces created between spaces

spaces are caused to expand and become less dense

relatively high mp: strong hydrogen bonding between the molecules

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11
Q

what is bonds between iodine

A

is a covalently bonded molecule (covalent bond is very strong)

weak induced dipole/ van der waal’s forces between molecules which gives crystal structure

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12
Q

iodine properties (5)

A

shiny grey at room temperature

Low melting point- weak vane dear wall’s forces are very easily broken but I2 molecules stay intact

Sublime(s=>g) when heated the grey solid turns into purple gas

Slightly soluble in H2O- b/c I2 is non-polar

Only in potassium iodide solution and iodide ions allows it to dissolve

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13
Q

structure of diamond

A

Each C atom form 4 single covalent bonds with 4 other C atoms

Tetrahedral arrangement (109.5)

Forms a 3d lattice of solid carbon

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14
Q

properties of diamond

A

Very hard: Due to the structure of double carbon covalent bonds

Very high melting point: Due to strong double carbon bonds, require a a lot of energy to break

Electrical insulation: All electrons involved on bonding/ no delocalised e-

Insoluble: Due to strong double carbon bonds

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15
Q

structure of graphite

A

Each carbon forms 3 single covalent nods with 3 other carbons

4th is delocalised

Trigonometry planar shape (120)

Forms a 2d hexagonal structure with delocalise delctrons

Weak van dear ewaals forces between the layers

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16
Q

properties of graphite

A

soft: due to weak van dear wall’s forces therefore layers can slide over each other

Very high melting point- strong double carbon covalent blonds therefore requires a lot of energy to break

Electrical conductor- delocalised elctrons are able to carry a current

Insoluble due to strong strong double cc bonds

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17
Q

what is a metallic bond

A

occurs between pure metals and alloys

A regular lattice of cations surrounded by a sea of delocalised electrons

Has non-directional electrostatic attractions between these

forms a metallic crystal structure

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18
Q

properties of metallic crystal structure

A

High melting points: due to strong electrotatics attractions

Conducts electricty: delocalised delctrons free to carry a charge

Conducts heat: delocalised elcetrons quickly transfer energy

Malleable/ductile: delocalised elctrons able to move with the ions when moved so don’t remove non-directional electrostatic attractions hence able to change shape.

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19
Q

what are trends in mp in metallic crystal structure

A

variations:

increases across a period due to increasing charge on ions

Decreases down a group due to increased shielding

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20
Q

what is VESPR

A

Valence shell electron pair repulsion

Used to determine the shapes of covalent molecules with 3 or more atoms

Molecules can contain both:

bonding pairs (covalent, coordinate, double, triple) and Lone pairs (unbounded electron pairs on the central atom)

repulsion: electron pairs repel each other and settle in a position to minimise repulsion i.e maximisawe bond angle

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21
Q

list of most repulsive to least

A

lone pair-lone pair

lone pair- bonding pair

bonding pair-bonding pair

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22
Q

3D structure notation:

methane

A
23
Q

what shape does these electron pairs make:

2 bonding pairs and no lone pairs

A

linear

24
Q

what shape does these electron pairs make:

2 bonding pairs and 2 lone pairs

A

bent

25
Q

what shape does these electron pairs make:

3 bonding pairs and no lone pairs

A

trigonal planar

26
Q

what shape does these electron pairs make:

3 bonding pairs and 1 lone pairs

A

trigonal planar

27
Q

what shape does these electron pairs make:

4 bonding pairs and no lone pairs

A

tetrahedral

28
Q

what shape does these electron pairs make:

5 bonding pairs and no lone pairs

A

trigonal bipyramidal

29
Q

what shape does these electron pairs make:

6 bonding pairs and no lone pairs

A

octrahedral

30
Q

what shape does these electron pairs make:

4 bonding pairs and 2 lone pairs

A

square planar

31
Q

how to find shape of unknowns

A

1) Decide central atom
2) Count valence e-
3) Count e- used by outer atoms to make bonds with central
4) Sum of 2) and 3) and divide by 2 = 2 VSEP
5) Use no. of BP and LP to predict geometry

32
Q

how to find bond angles of unknowns in larger molecules

eg ethanol

eg hydrazine

eg glucose

A

split molecule into smaller version as the overall shape is going to be combined

33
Q

find bonding angles of :

ethanol (C2H5OH)

A

1) Find the h-c-h bond angle where 4 BP(+0LP) around central c atom

Tetrahedral therefore 109.5

2) Find the c-o-h bond angle where 2 BP +2 LP around the central o atom

Bent therefore 104.5

34
Q

find bond angles of:

hydrazine (N2H4)

A

1) Find the h-n-h bond angle wher 3 BP + 1LP around the central n atom

Trigonal pyramidal therefore 107

(happens twice)

35
Q

find bond angles in:

glucose (C6H12O6)

A

1) C-c-c bond angle is 109.5

3 BP around c atom trigonal planar

2) C-o-c bond angle =104.5

36
Q

what is electronegativity

A

the power of an atom to attract a bonding pair of electrons

37
Q

trends on periodic table with electronegativity

A
  • Where the least negativity is low effective charge = on nucleus and high shielding
  • where the most electronegativity is high effective charge= on nucleus and low shielding

Group 8 is discounted b/c full outer shell therefore not reactive

38
Q

how does elctronegativity affect bonding in

A

what: Electrons are shared equally
why: electronegativity is the same
properties: Non-polar, No di-pole, 2 of the same element
eg. H2, N2, F2

39
Q

how does electronegativity affect

a) covalent
b) ionic

bonding

A

Covalent- a difference in electronegativity causes pairs of electrons in a bond to be shared unequally

Ionic- difference in elctronegativity so big so elctrons are transferred

40
Q

how does electronegativty affect bonding in

A

what: Electrons shared unequally
why: Y has a greater electronegativity so BP of e- drawn towards it
properties: Polar, Dipole, 2 elements that are different

41
Q

how does electronegativity affect in

A

what: electrons shared unequally in favour of X
why: Large difference in electronegativity

Specifically: h-f, h-o, h-n

properties: Polar, Dipole, Hydrogen bonding

42
Q

what are induced dipole forces

A

Occur between all molecules

Weakest intermolecular forces

Strength varies- increased with increasing Mr (more electrons involved)

43
Q

examples of induced dipole forces (3)

A

eg. monatomic elements, cannot be polar because no elctronegativity
eg. Diatomic elements, have no permanent dipole because atoms have same elctronegativity

Eg larger non-polar molecules, moloceules are symmetrical therefore. No obvious poles (f+ f-)

All these examples show increasing strength of imf with increased mr

Therefore show increased mp/gp as more energy needed to break imf

44
Q

what are permanent dipole forces

A

occur between polar molecules

Stronger that induced dipole forces but weaker than h bonding

Causes these compounds to have a higher than expected mp/bp

45
Q

example of permanent dipole forces

A
46
Q

what is hydrogen bonding?

A

occurs between molecules taht contain a H atom directly bonded to N, O or f

strongest IMF

(basically just a really strong dipole)

47
Q

hydrogen bonding in simple molecules

eg. hydrogen fluoride

eg water

eg ammonia

A

causes compounds to havre a much greater mp/ bp than expected

48
Q

trends of compounds with hydrogen bonding

A

increases due to increased mr

anomalies due to hydrogen bonding

49
Q

hydrogen bonding in organic molecules

eg. alcohols

eg carboxylic acids

eg. amines

A
50
Q

example 1 of comparing mp/bp

which has higher mp/bp

A
51
Q

example 2 of comparing mp/bp

which has higher mp/bp

A
52
Q

example 3 of comparing mp/bp

which has higher mp/bp

A
53
Q

example 4 of comparing mp/bp

which has higher mp/bp

A

chem (13 decks)

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