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bonding Flashcards

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1
Q

what are cations?

A

positively charged ions

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2
Q

what are anions?

A

negatively charged ions

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3
Q

what is an ionic bond

A

electrostatic attractions between oppositely charged ions which occurs in all directions

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4
Q

why do ionic bonds have high melting points

A

the electrostatic forces of attraction are very strong and require a lot of energy to overcome

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5
Q

how do ions form

A

when electrons are transferred between elements that have a high difference in electronegativity ie metals (which lose electrons to become positively charged cations) and non-metals (which gain electrons to become negatively charged anions)

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6
Q

what structure do ions form?

A

a regular lattice of alternating positively charged and negatively charged ions held together by electrostatic forces of attraction

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7
Q

5 properties of ionic crystal lattices

A
  • very high melting point: due to strong electrostatic forces of attraction holding the ions together requiring a lot of energy to break
    -electrical insulators when solid: ions are fixed in place and cannot carry a charge
  • electrical conductors when molten/ in aqueous solution- ions are free to move around and so can carry a charge
    -brittle- when moved ions no longer have an alternating arrangement, meaning they repel eachother and the lattice breaks
    -generally soluble in h20- h2o is very polar so can disrupt the electrostatic attractions betwen the ions and break them up
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8
Q

what type of atoms does ionic bonding happen between

A

metals and non-metals

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9
Q

what kinds of atoms does covalent bonding occur between?

A

between elements with high electronegativity values /non-metals

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10
Q

what kind of atoms does metallic bonding occur between?

A

metals

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11
Q

what is a covalent bond?

A

a shared pair of electrons with opposite spins, one electron is donated from each atom

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12
Q

what kind of forces are involved within a covalent bond?

A

the donated electrons are an area of high electron density/are highly negative
strong attractions between electrons and positive nuclei

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13
Q

what is a co-ordinate bond also known as?

A

dative covalent bond

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14
Q

what is a co-ordinate bond

A

a covalent bond that is formed when both electrons are donated from the same atom (between a lone pair of electrons and an electron deficient atom)

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15
Q

why is ice less dense than water?

A

below 0°C, molecules have less energy so the hydrogen bonds fix in position. ice has a 3d hexagonal crystal structure. spaces are created between the molecules causing it to expand and become less dense

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16
Q

why does h20 have a relatively high melting point?

A

strong Hydrogen bonds between molecules

17
Q

what kind of forces exist between molecules of iodine?

A

weak induced dipole-dipole forces/ van der waal’s forces

18
Q

properties of iodine

A

-shiny grey solid at room temp
-low melting/boiling point- weak van der waal’s forces are easily broken
-sublimes - when heated the grey solid turns into a purple gas
-slightly soluble in h2o- I2 is non-polar

18
Q

what are diamond and graphite?

A

allotropes of carbon

19
Q

structures of diamond and graphite?

A

diamond: each carbon atom is covalently bonded to 4 other carbon atoms, forming a giant covalent lattice structure with tetrahedral arrangements/shapes
graphite: each carbon atom is covalently bonded to 3 other carbon atoms with the 4th carbon being delocalised to form layers of graphene arranged in hexagonal shapes. layers of graphene are held together by weak van der waal’s forces of attraction

20
Q

properties of diamond

A

-very hard: due to structure of strong C-C covalent bonds
- high melting point: strong covalent C-C bonds require a lot of energy to break
-electrical insulator: all electrons involved in bonding (no delocalised electrons)
-insoluble- strong C-C bonds / no polarity

21
Q

properties of graphite

A

-soft: weak VDW’s forces fo attraction graphene layers can slide over one another
-very high melting point: strong C-C covalent bonds require a lot of energy to break
-electrical conductor- delocalised electrons are able to carry a charge/current
-insoluble: strong C-C bonds

22
Q

what is a metallic lattice

A

a regular lattice of cations surrounded by a ‘sea’ of delocalised electrons.
electrostatic forces of attraction between ions and electrons

23
Q

protperties of metallic lattices

A
  • high melting points: due to strong electrostatic attractions (variations: increases across a period because there is an increased charge on the ions/ decreases down a group because of increased shielding)
    -conduct electricity: delocalised electrons can carry a charge
    -conduct heat: delocalised electrons quickly transfer energy
    -malleable/ductile: delocalised electrons can move with the ions when moved as they maintain the non-directional electrostatic attractions and hence the shape
24
Q

define electronegativity

A

the power of an atom to attract electrons in a covalent bond

25
Q

what is a polar covalent bond

A

a bond with unequal distribution of electrons due to a difference in electronegativity of the bonding atoms

26
Q

order of strength of intermolecular forces from stronger to weakest

A

hydrogen bonds
permanent dipole-dipole
induced dipole-dipole

27
Q

what molecules do induced dipole-dipole forces occur between?

A

all molecules

28
Q

what molecules do hydrogen bonds happen between?

A

hydrogen and oxygen/nitrogen/fluorine

29
Q

what are induced dipole-dipole forces of attraction?

A

temporary intermolecular forces of attraction caused by temporary dipoles ( which exist when the constantly moving electron clouds cause partial charges to form) which exert a force on nearby molecules. the partial charge of one molecule can push or attract towards it the electrons from another molecule/

30
Q

trend in strength of induced dipole-dipole forces of attraction

A

becomes stronger with increasing Mr as more electrons are involved
since more energy is then needed to overcome it, melting and boiling points increase with increasing Mr

31
Q
A

Chemistry (10 decks)

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