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Chemistry-Module 2 > 2.2.2-Bonding and structure > Flashcards

2.2.2-Bonding and structure Flashcards

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1
Q

ionic bonding

A

strong electrostatic force of attraction between oppositely charged ions

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2
Q

describe which compound will have a higher charge Sodium chloride or Magnesium oxide

A

-The greater the charge
on the ions, the stronger the forces holding them together
-Sodium chloride is made from Na+ ions and Cl– ions and has a melting point of 801°C
-Magnesium oxidemade from ions with two charges (Mg2+ and O2–) and so has a much higher melting point of 2,852°C.

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3
Q

covalent bonding

A

the strong electrostatic force of attraction between a shared pair of electrons and nuclei of bonded atoms

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4
Q

dative(coordinate bonding)

A

when both electrons come from same atom

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5
Q

define average bond enthalpy

A

measurement of covalent bond strength

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6
Q

electronegativity

A

the ability of an atom to attract bonding electors I a covalent bond

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7
Q

the three types of intermolecular forces are:

A

-the permanent dipole-dipole interactions
-induced dipole-dipole interactions
-hydrogen bonding

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8
Q

hydrogen bonding

A

-bonding between N,O or F

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9
Q

describe two anomalous properties due to hydrogen bonding

A

-ice is less dense than liquid water due to water molecules pushed further apart forming an open lattice structure
-has relatively high melting and boiling point due to the hydrogen bonding

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10
Q

describe what are simple molecular lattices

A

-covalently bonded molecules attracted by London forces

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11
Q

structure of ice

A

-simple molecular lattice
-the covalently bonded molecules are attracted by the hydrogen bonds

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12
Q

metallic bonding

A

strong electrostatic attraction between cations(positive metal ions) and a sea of delocalised electrons

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13
Q

describe the structure of diamond graphite graphene and silicon

A
  • a network of atoms bonded by strong covalent bonds
    -giant covalent lattice
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14
Q

describe a polar bond

A

-occurs within molecules containing covalently bonded atoms with a permanent dipole due to the large difference in electronegativities

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15
Q

compound

A

two or more elements that are chemically bonded together

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16
Q

describe why noble gases are stable

A
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17
Q

lone pair

A

an unshared pair of electrons that is not involved in bonding

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18
Q

outline why ionic compounds are naturally soluble in water

A

-they are both polar and so is water

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19
Q

what do the Pauling values represent

A

non-polar= 0
polar= 0-1.8
ionic= more than 1.8

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20
Q

describe why a compound is non-polar

A

-it is symmetrical
-has an even distribution of charge

21
Q

describe why simple covalent molecules have relatively low melting and boiling points

A

-the intermolecular forces between covalent molecules are weak-london forces
-do not require much energy to break
-low melting and boiling points and are generally liquids and gases at rtp

22
Q

what is broken in giant covalent molecules

A

the strong covalent bonds

23
Q

where are London forces found

A

found between all molecules

24
Q

why can water form two hydrogen bonds per molecule

A

oxygen very electronegative
and has two lone pairs of electrons
molecules ae held further apart than in liquid so lower denisty in ice

25
Q

why are permanent dipole -dipole forces strronger than london forces

A

-permanent dipole-dipole forces occur betwen polar molecules
-they are asymmetrical and due to the significant difference in electronegativity ina ddition to london forces it makes it stronger
-so higher boiling points

26
Q

Explain why I2 solid but Cl2 gas

A

-the increasing boiling points as you go down group
-due to increasing number of electrons in bigger molecules causing an increase in size of induced dipole-dipole interactions between molecules

27
Q

explain why CO2 is symmetrical

A

molecule is non-polar
all dipoles on bonds ‘cancel out’ due to symmetrical shape of molecule
there is no net dipole movement -molecules is non polar

28
Q

what determines shape of a molecule

A

-by the number of electron pairs around central atom and repulsion between them
-each electron pair naturally repel
-so largest bond angle possible exists

29
Q

why are double and triple bonds stronger than a single covalent bond?

A

-the length of a covalent bond is strongly linked to its strength
-shorter bonds stronger as aroms held closer together
forces of attraction greater
higher levels of enrgy to break

30
Q

Graphene

A

Bonding- has strong covalent bonds between atoms and delocalised electrons across its surface

E.C-Yes,as the delocalised electrons can move

T.B- High,strong covalent bonds between atoms require a lot of energy to break

31
Q

Graphite

A

Bonding-strong covalent bonds between carbon atoms and weak London forces between layers,
Also has delocalised electrons which can move between layers
Trigonal planar-120

E.C-Yes,as delocalised electrons can move

T.B- High, as covalent bonds between atoms require a lot of energy to break
layers of carbon atoms that are arranged in 6-membered, hexagonal rings.

32
Q

Diamond

A

Bonding-strong covalent bonds between the carbon atoms, every carbon has 4 carbons attached so tetrahedral-109.5

electrical conductivity-no, there are no delocalised electrons

melting and boiling point-high,strong covalent bonds between atoms require a lot of energy to break

33
Q

what are simple molecular substances?

A

-Made up of molecules containing a few atoms joined together by covalent bonds
-in non-metals

34
Q

Simple molecular -e.g.I2

A

Bonding-strong covalent bonds between atoms ,weak intermolecular forces between molecules

E.C-No,there are no delocalised electrons

Melting point and boiling point-low, as there are weak intermolecular forces between molecules

35
Q

Giant metallic lattice-e.g Na

A

Bonding-positive metal ions attracted to a sea of delocalised electrons

Electrical conductivity-Yes, as the delocalised electrons are free to move

Tm and Tb-High,due to the strong electrostatic forces of attraction between the positive ions and delocalised electrons

36
Q

Giant ionic lattice-e.g LiCl

A

Bonding-strong electrostatic force of attraction between oppositely charged ions

Electrical conductivity-Yes, only when molten or dissolved as ions are free to move
No,when solid as ions cannot move

Tm and Tb-High due to strong electrostatic forces of attraction between oppositely charged ions

37
Q

what do non-metals in periodic table form?

A

-covalent bonding
1-giant molecule or macromolecular-covalent bonding- throughout the structure-diamond,graphite,silicon dioxide

2-simple molecule molecular-weak intermolecular forces-carbon dioxide and water

38
Q

Properties of compounds with Hydrogen Bonding

A

*They have higher boiling points compared to compounds the other types of intermolecular forces
*They tend to be soluble in other compounds with hydrogen bonds (water, ethanol) eg ammonia, HF, carboxylic acids will dissolve in water and ethanol.
*They can have higher viscosity: the stronger the hydrogen bonding the more viscous the liquid.
*Higher surface tension

39
Q

Why does hydrogen bonding explain why water has a high surface area tension and viscosity?

A

water molecules are less capable to slide over each other so that water has a high viscosity.
The hydrogen bonds at the surface of water gives rise to surface tension

40
Q

why are hydrogen bonds stronger than the other two types of intermolecular bonds?

A

-The small size of the hydrogen atom and the oxygen,nitrogen, fluorine atoms allow the atoms to approach eachother closely, which makes the force of attraction strong.
-The force of attraction is also made strong because the difference in electronegativity is significant.

41
Q

what are permanent dipole-dipole forces

A

the weak intermolecular forces of attraction that arise between permanently polar molecules

for example Hal

42
Q

how do induced dipoles-london forces occur

A
  • movement of electrons within orbital can trigger dipoles in a molecule
  • instantaneous dipoles will exist but it will be constantly shifting
  • instantaneous dipole induces a dipole in a neighbouring molecule
  • induced dipole induces further dipoles
43
Q

Why is the CF4 molecule nonpolar even though it contains polar bonds?

A

All bond dipoles are painting away from C toward F because F is the more electronegative atom .These dipoles cancel out

44
Q

Factors that affect size of London forces

A

1-more electrons there are in the molecule the higher the chance that temporary dipoles will form.
This makes the London forces stronger between the molecules and more energy is needed to break them so boiling points will be greater.
2-The shape of the molecule can also have an effect on the size of the London forces. Long straight chain alkanes have a larger surface area of contact between molecules for London forces to form than compared to spherical shaped branched alkanes and so have stronger London forces .

45
Q

How do London forces occur?

A

-In any molecule the electrons are moving constantly and randomly.
- As this happens the electron density can fluctuate and parts of the molecule temporarily become more or less negative i.e. small temporary or transient dipoles form.

46
Q

intermolecular forces

A

forces of attraction between molecules

47
Q

bond enthalpy

A

the energy required to break a bond present in a compound.

48
Q

Why do lone pairs repel more than bonding pairs?

A

-lone pairs are not shared by two atoms, so they are held closer to the nucleus
-this means they repel further than a bonded pair of electrons

Chemistry-Module 2 (7 decks)

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