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A-LEVEL CHEM > BONDING > Flashcards

BONDING Flashcards

1
Q

State how ions form and why they attract each other

A
  • Ions form when atoms lose or gain electrons
  • Since electrons are negatively charged, an atom that loses one or more electrons will become positively charged
  • An atom that gains one or more electrons will become negatively charged
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2
Q

What’s ionic bonding

A

Bonding that involves electrostatic attraction between oppositely charged ions in a lattice

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3
Q

Formula of sulfate ion

A

SO₄²-

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4
Q

Formula of hydroxide ion

A

OH¯

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5
Q

Formula of nitrate ion

A

NO3-

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6
Q

Formula of carbonate ion

A

HCO3-

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7
Q

Formula of ammonium ion

A

NH₄⁺

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8
Q

State the properties of ionically bonded compounds

A
  • High melting and boiling points > ions in giant ionic lattice are held by strong electrostatic forces of attraction acing in all directions> difficult to overcome
  • Conduct electricity when molten or dissolved in solution > ions of the compound are able to move and carry charge. Unable to conduct when solid as ions are fixed in place so unable to carry charge
  • Soluble in water > both ionic compounds and water molecules are partially charged molecules (polar). > means the partial charges of water break apart the ionic lattice, pulling oppositely charged ions apart and the ionic compound to dissolve.

-Always solids at room temperature > have giant structures and therefore high melting temperatures > in order to melt an ionic compound, a lot of energy is required to break up the lattice of ions

  • Brittle and shatter easily when given a sharp blow > they form a lattice of alternating positive and negative ions
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9
Q

Describe the structure of ionically bonded compounds

A

The structure of this ionic compound is a giant lattice with oppositely charged ions and strong electrostatic forces (attractive forces between ions) between them

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10
Q

Describe a covalent bond

A
  • Forms between 2 non-metals
  • Atoms share some of their outer electrons so that each atom has a stable noble gas arrangement
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11
Q

Describe a co-ordinate bond (dative covalent)

A
  • Bonds contains a shared pair of electrons with both electrons supplied by one atom
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12
Q

Describe the properties of covalently bonded molecules

A
  • Substances composed of molecules are gases, liquids, or solids with low melting points > the strong covalent bonds are only between the atoms within the molecules > there’s only a weak attraction between the molecules so the molecules don’t need much energy to remove the bonds
  • Poor electrical conductors > molecules are neutral overall > no charged particles to carry current
  • When dissolved in water, they remain as molecules > solutions don’t conduct electricity > no charged particles
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13
Q

Define electronegativity

A

measure of tendency of an atom to attract a bonding pair of electrons in a covalent bond

-greater the e.n. of an atom the more it attracts electrons towards it

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14
Q

Factors that affect electronegativity of an atom

A

-atomic charge
-distance from nucleus (atomic nucleus)
-electron sheilding

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15
Q

Non-polar covalent bonds

A

no difference between electronegativities e.g. Cl-Cl

-symmetrical molecules are non-polar even though they contain polar bonds

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16
Q

Polar covalent bonds

A

Small difference between electronegativities e.g. H-Cl

17
Q

Ionic bond

A

Large difference in electronegativities

18
Q

Difference between intermolecular and intramolecular forces

A

Intermolecular - attractive forces between neighbouring molecules

intramolecular -bonds that act WITHIN one molecule

19
Q

Linear shape

A
  • Total number of electron pairs = not applicable
  • 1 bonding pair of electrons
  • lone pairs not applicable
  • bond angle = 180
    -e.g. H2 and HCL
20
Q

Linear Shape (2)

A
  • Total number of electron pairs = 2
  • 2 bonding pair of electrons
  • 0 lone pairs
    -180
    -e.g. C02 HCN
21
Q

Trigonal Planar

A
  • 3 electron pairs
  • 3 bonding pairs
  • 0 lone pairs
    -120
    e.g. Al, Cl3, Bcl3
22
Q

V-shaped/ bend/ non linear

A
  • 4 electron pairs
    -2 bonding pairs
  • 2 lone pairs
    -104.5
    -e.g. H2O
23
Q

Tetrahedral

A

-4 electron pairs
-4 bonding pairs
-0 lone pairs
-109.5
-e.g. CH4

24
Q

Triangular pyramid

A

-4 electron pairs
-3 bonding pairs
-1 lone pair
-107
-e.g. NH3

25
Q

Triangular bi pyramidal

A

-5 electron pairs
-5 bonding pairs
-0 lone pairs
-90 and 120
-e.g. PCl5

26
Q

Octahedral

A

-6 electron pairs
-6 bonding pairs
-0 lone pairs
-90
-e.g. SF6

27
Q

How do van der waal forces occur

A

-uneven distribution of electrons creates a temporary dipole
-this induces a dipole in the neighbouring atom/molecule
-causes an attraction between diples

28
Q

Why are van der waal forces stronger in larger molecules

A

more electrons

29
Q

What’s permanent dipole dipole

A

weak attractive force between permanent dipoles in neighbouring polar molecules

30
Q

What’s hydrogen bonding

A

Strong forces of attraction between H nucleus and lone pair of electrons on O,N / F

31
Q

Conditions needed for H bonding to take place

A

-Bonded to strongly electronegative elements (F,O,N)
-electronegative elements MUST have at least a lone pair of electrons

32
Q

Explain hydrogen bonding in hydrogen fluoride

A

-In HF, the fluorine atom has 3 lone pairs of electrons
-F is the most electronegative elements so strongly attracts the lone pair of electrons in a covalent bond
-therefore molecule is polar with H atom having a + charge

33
Q

Why’s ice less dense than water

A

-In water, water molecules are constantly moving randomly (molecules far or sometimes close) and so H bonds are constantly being broken and reformed.
-As water cools, molecules move more slowly
-when reach freezing point, H2O molecules arrange themselves in fixed positions (ice) and this is stabilised by the network of H bonds
-H2O molecules in ice are further apart than in liquid as they’re in fixed positions

34
Q

Why’s ice less dense than water

A

-In water, water molecules are constantly moving randomly (molecules far or sometimes close) and so H bonds are constantly being broken and reformed.
-As water cools, molecules move more slowly
-when reach freezing point, H2O molecules arrange themselves in fixed positions (ice) and this is stabilised by the network of H bonds
-H2O molecules in ice are further apart than in liquid as they’re in fixed positions

A-LEVEL CHEM (20 decks)

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