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chem > bonding notes > Flashcards

bonding notes Flashcards

1
Q

Metallic Structure and Bonding

A

giant metallic lattice
strong electrostatic attraction between positive metal ions and delocalised electrons

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2
Q

The bonding in Magnesium is stronger than in Sodium because:

A

Mg has a greater charge of 2+

Mg has twice as many electrons in the sea of delocalised electrons

Mg ions are smaller, greater charge density

therefore, attraction between Mg2+ ions and delocalised electrons is stronger

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3
Q

properties of metals:

A

conductivity:
electrical and thermal conductors delocalised electrons to transfer current

strength:
strong electrostatic attraction between positive metal ions and sea of delocalised electrons

malleable and ductile:
hammered into shape
pulled into wires
rows of metal ions can slide past one another

melting and boiling points:
strength of metallic bonds;
stronger they are;
higher mp and bp

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4
Q

Covalent Structure and Bonding

A

macromolecular and simple
molecular

A covalent bond is a shared pair of electrons between two atoms

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5
Q

macromolecular structures:

A

silicon
carbon
silicon oxide

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6
Q

Diamond:

A

Each C has 4 covalent bonds
tetrahedral shape
very high mp
very hard
non conductor (no delocalised electrons)

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7
Q

graphite:

A

layers with 3 covalent bonds to each C atom
each C has a delocalised electron
layers held together by weak intermolecular forces
soft layers can slide over one another
conductor has delocalised electrons
mp high

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8
Q

forces and properties of simple molecular structures;

A

IMFs act between molecules

melting causes breaking of IMFs

IMFs weaker than covalent bonds

low MP

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9
Q

Ionic structure and bonding:

A

Giant ionic lattice

strong electrostatic attractions between oppositely charged ions

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10
Q

Physical and structural properties of ionic compounds:

A

high mp and bp

electrical conductivity - aqueous or molten

brittle and shatter easily

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11
Q

ammonium:

A

NH4+

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12
Q

hydroxide

A

OH-

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13
Q

nitrate

A

NO3-

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14
Q

nitrite

A

NO2-

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15
Q

hydrogencarbonate

A

HCO3-

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16
Q

Chlorate(I)

A

CIO-

17
Q

Chlorate(v)

A

CIO3-

18
Q

carbonate

A

CO32-

19
Q

sulfate

A

SO42-

20
Q

sulfite

A

SO32-

21
Q

dichromate

A

Cr2O72-

22
Q

phosphate

A

PO43-

23
Q

Coordinate bonds

A

A coordinate bond is a shared pair of electrons which have both come from the same atom

24
Q

Define electronegativity

A

the ability of an atom to attract electron density from a covalent bond

25
Q

The factors which determine how electronegative an element are:

A

nuclear charge

the atomic radius

the shielding

26
Q

why is fluorine the most electronegative?

A

as you go UP groups - electronegativity INCREASES because radius and amount of shielding DECREASES

as you move ACROSS a period - electronegativity INCREASES beaches the nuclear charge INCREASES and the radius DECREASES

27
Q

what are the three types of intermolecular forces?

A

induced dipole dipole (van der waals forces)

permanent dipole dipole

hydrogen bonding

28
Q

when does hydrogen bonding occur?

A

occurs between H and lone pair on either: N, O, F

strongest IMF

29
Q

how does hydrogen boding arise?

A

very large difference in electronegativity between Oxygen (NOF) and H

creates a dipole on the O-H bond

lone pair on oxygen atom in one molecule strongly attracts a partially positive H on a different molecule

30
Q

when do permanent dipole dipole forces occur?

A

between polar molecules

generally weaker than hydrogen bonding

31
Q

how do permanent dipole dipole forces arise?

A

difference in electronegativity leads to bond polarity

dipoles don’t cancel out, therefore the molecule has an overall permanent dipole

there is an attraction between s+ on one molecule and s- on another

32
Q

when do induced dipole dipole forces (VDWs) occur?

A

occurs between all molecules but most important for non polar molecules

generally the weakest force but can be stronger than hydrogen bonding and permanent dipole dipole if molecule is large enough = lots of electrons

33
Q

how do induced dipole dipole occur?

A

Random movement of electrons in one molecule leads to…

Uneven distribution of electrons, creating a…

Temporary dipole in one molecule…

Induces dipole in a neighbouring molecule

Dipoles attract

34
Q

importance of hydrogen bonding

A

ice: less dense than water because the hydrogen bonds in ice hold the molecules further apart

proteins: they’re held in their complex 3D shapes by hydrogen bonds
the shape of a protein is vital for its function

DNA: carries all genetic information of living things
the two strands in the double helix are held together by hydrogen bonds
strong enough to hold together and weak enough to allow strands to separate for semi conservative replication

35
Q

physical properties in period 3 elements
mp and bp (na to mg to al)

A

increases

strong attraction between cation and delocalised electrons

charge on ion increases

size decreases

more delocalised electrons

36
Q

physical trends in period 3 elements :
silicon

A

macromolecular

to melt Si many strong covalent bonds must be broken

which requires a large amount of energy

therefore Si has the highest MP

37
Q

physical trends in period 3 elements :
P, S, Cl

A

simple molecular

P4 S8 Cl2

covalent bonding between atoms

VDWs forces between molecules

weak forces

S8 slightly highest MP and BP = greater electrons

S8>P4>Cl2

38
Q

physical trends in period 3 elements :
Ar

A

monoatomic

no bonding

weakest vdws between atoms

least amount of e-

smallest

chem (9 decks)

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