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Giant Flashcards

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1
Q

Metallic bonding

A

The electrostatic attraction between POSITIVE METAL IONS and the DELOCALISED ELECTRONS.

  • Atoms in metals lose their outer shell electrons to form POSITIVE IONS.
  • The electrons are shared between all atoms in the metallic structure.
  • A single electron is attracted to all the CATIONS surrounding it in the lattice.
  • The metallic bonds act in ALL DIRECTIONS.
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2
Q

Metallic structure

A
  • Metals form a :
    GIANT METALLIC LATTICE STRUCTURE

-They form a 3D arrangement of positive metal ions bonded to delocalised electrons via metallic bonds.

  • The delocalised electrons are found THROUGHOUT the structure.
  • The ORIGIN of each electron is UNKNOWN.
  • The total positive charge from the metal ions is EQUAL to the total negative charge from the electrons.
  • This means metals have an overall NEUTRAL CHARGE.
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3
Q

Metallic - HIGH MP & BP

A
  • There is a STRONG electrostatic attraction between positive metal ions and the delocalised electrons.
  • This means HIGH TEMPERATURES are needed to overcome them.
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4
Q

Metallic - HARD & STRONG

A
  • Metals have a LATTICE structure
  • This means the atoms in a metal are arranged in CLOSELY-PACKED layers.
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5
Q

Metallic - SHINY

A
  • The presence of delocalised electrons causes most metals to REFLECT LIGHT.
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6
Q

Metallic - MALLEABLE & DUCTILE

A
  • The MOBILITY of electrons in a metallic structure allow the metal ions to SLIDE OVER each other into NEW lattice POSITIONS.
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7
Q

Metallic- HIGH DENSITY

A
  • All ions are pulled tightly together and closely packed.
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8
Q

Metallic - CONDUCT HEAT & ELECTRICITY

A
  • The delocalised electrons are FREE to move through the metallic lattice.
  • VIBRATIONS of positive ions also takes place.
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9
Q

Metallic - SOLUBILITY

A
  • Metals DO NOT dissolve.
  • The interaction of the delocalised electrons and the metal cations with a POLAR solvent may lead to a REACTION.
  • But it is NOT DISSOLVING.
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10
Q

Simple molecule

A

Atoms are joined together by COVALENT BONDS and there are WEAK intermolecular forces between the molecules.

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11
Q

PROPERTIES of simple molecular structures

A

RELATIVELY LOW MP & BP:
- Little energy is required to overcome the IMF between the molecules.

DO NOT CONDUCT ELECTRICITY:
- Do not contain any mobile charged particles.

SOLUBILITY:
- Depends on whether the substance is polar or non-polar.

  • Non-polar substances will dissolve in non-polar solvents ~ the solvent molecules form LONDON FORCES with the non-polar substance.
  • This means that non-polar substances are usually INSOLUBLE in polar solvents ~ this is because the hydrogen bonds in the polar substance remain rather than forming London forces with the non-polar substance.
  • Polar substances dissolve in polar solvents ~ this is because the same IMF are acting in the solvent and substance.
  • This means that polar substances are usually insoluble in no-polar solvents
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12
Q

Iodine

A
  • There are STRONG COVALENT bonds within the I2 molecules.
  • There are WEAK INTERMOLECULAR FORCES ( London ) between the I2 molecules which require LITTLE ENERGY to overcome.
  • It is a NON-POLAR molecule meaning it can dissolve very well in non-polar solvents.
  • The I2 molecules are found in a regular repeating pattern in the solid , forming a LATTICE STRUCTURE.
  • This means iodine forms a SIMPLE MOLECULAR LATTICE STRUCTURE.
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13
Q

Water

A

IN ITS SOLID FORM (ice) :
- Forms a simple molecular lattice structure whereby water molecules are held together by hydrogen bonds.

  • Ice has a lower density than water allowing it to float.
  • HIGH MP & BP ~ a large amount of energy is needed to overcome the hydrogen bonds.
  • POLAR molecule meaning it is soluble in substances that are also polar.

Water exists as a simple molecular structure when it is both a LIQUID & GAS.

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14
Q

Allotrope

A

Where atoms of the same element can exist in different STRUCTURAL FORMS whilst in the same PHYSICAL STATE.

Example ~ Diamond and graphite are two ALLOTROPES of CARBON.

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15
Q

BONDING in Diamond

A
  • A giant covalent lattice structure.
  • Each carbon atom in diamond is bonded to FOUR other carbon atoms.
  • The four bonding pairs of electrons around each carbon atom repel each other EQUALLY.
  • This leads to a bond angle of 109.5 degrees and a TETRAHEDRAL shape around each carbon.
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16
Q

Diamonds PROPERTIES

A

POOR CONDUCTOR:
- The outer electrons in the carbon atoms are all involved in covalent bonding.
- This means their are NO delocalised electrons.

HARD & STRONG:
- Strong covalent bonds between the carbon atoms.

17
Q

Does WATER or DIAMOND have a higher melting point?

                   EXPLAIN
A

DIAMOND has the higher melting point.

IN ICE:
- A low temperature provides enough energy to break the IMF :
- hydrogen bonds
- permanent dipole-dipole forces
- London forces.

IN DIAMOND:
- Very large amounts of energy is required to break the strong covalent bonds.
- Diamond has both a high MP & BP

18
Q

BONDING in Graphite

A
  • Giant covalent lattice structure
  • Each carbon atom in graphite is bonded to THREE other carbon atoms.
  • The three bonding pairs of electrons around each carbon atom repel each other equally.
  • This leads to a bond angle of 120 degrees and a TRIGONAL PLANAR shape around each carbon.
19
Q

STRUCTURE of Graphite

A
  • The carbon atoms are bonded together to produce HEXAGONAL LAYERS.
  • The FOURTH outer electron in each carbon atom is not involved in covalent bonding and is DELOCALISED between the hexagonal layers.
  • The electrons give rise to WEAK LONDON forces between the layers.
20
Q

PROPERTIES of Diamond

A

CONDUCTS ELECTRICITY:
- The delocalised electrons can move PARALLEL to the hexagonal layers of carbon atoms when a voltage is applied.

SOFT:
- The layers can easily SLIDE over each other .
- Due to the LONDON FORCES between the layers.

21
Q

GENERAL PROPERTIES of Giant Covalent Structures

A

HIGH BP & MP:
- Lots of energy required to break the covalent bonds.

INSOLUBLE IN POLAR & NON-POLAR SOLVENTS:
- The solvents cannot break the covalent bonds.

DO NOT CONDUCT ~ EXCEPT for graphite and silicon.

22
Q

Graphene

A
  • TWO-DIMENSIONAL giant covalent lattice structure.
  • ONE CARBON THICK and consists of interlocking hexagonal rings of carbon atoms.
  • Extremely STRONG & very LIGHT
  • CONDUCTS ELECTRICITY as it has delocalised electrons.
23
Q

Does MAGNESIUM or SODIUM have the HIGHER MP

A

MAGNESIUM has the higher melting point.

  • Na atom loses one electron to form Na+ ions.
  • Mg loses TWO electrons to form Mg2+ ions.
  • The ELECTROSTATIC ATTRACTION between Mg2+ ions and the delocalised electrons is …
  • Than the Na+ ion and delocalised electrons.
  • Mg has a STRONGER METALLIC bond which requires more energy to overcome.

Chemistry (12 decks)

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