3 bonding Flashcards Preview

A Level Chemistry > 3 bonding > Flashcards

Flashcards in 3 bonding Deck (29):
1

ionic bonding

describes a chemical bond in which an electron(s) are transferred from one atom to another, resulting in the formation of oppositely charged ions with electrostatic forces of attraction between them in a lattice

2

covalent bonding

describes a chemical bond in which a pair of electrons are shared between two atoms

3

metallic bonding

describes a chemical bond in which there is attraction between positive metal ions and the sea of delocalised (outer) electrons in a lattice

4

lattice

a regular 3D arrangement of atoms, ions or molecules

5

co-ordinate bonding / dative covalent bonding

covalent bonding in which both the electrons in the bond come from one of the atoms in the bond

6

lone pair

a pair of electrons in the outer shell of an atom that is not involved in bonding

7

delocalised

describes electrons that are spread over several atoms and help to bond them together

8

electronegativity

the power/tendency of an atom to attract a bonding pair of electrons in a covalent bond

9

electron density

the probability of electrons being found in a particular volume of space

10

polarity

the unequal sharing of the electrons between atoms that are covalently bonded together - a property of the bond

11

polar

describes a molecule in which the charge is not symmetrically distributed so that one area is slightly positively charged and another slightly negatively charged

12

van der Waals/induced dipole-dipole/dispersion/London forces

a type of intermolecular force of attraction that is caused by instantaneous dipoles and acts between all atoms and molecules

13

dipole-dipole forces

an intermolecular force that results from the attraction between molecules with permanent dipoles

14

hydrogen bonding

a type of intermolecular force in which a (d+) hydrogen atom interacts with a more electronegative atom with a (d-) charge

15

electron pair repulsion theory

a theory which explains the shapes of simple molecules by assuming that pairs of electrons around a central atom repel each other and thus take up positions as far away as possible from each other in space

16

enthalpy

the heat energy change measured under constant pressure

17

temperature

the average kinetic energy of the particles and is therefore related to their speed - the greater the energy, the faster they go

18

enthalpy change of melting

the energy needed to weaken the forces that act between particles, holding them in the solid state, to turn a solid into a liquid (no temp change as heat energy provided is absorbed as forces between particles are weakened)

19

enthalpy change of vaporisation

the energy needed to break all the intermolecular forces between the particles to turn a liquid into a gas (no temp change as heat energy provided is absorbed as forces between particles are weakened)

20

simple molecular crystal structure

composed of small molecules - small groups of atoms strongly held together by covalent bonding. the forces of attraction between molecules are much weaker and are called intermolecular forces e.g. H2O, Cl2, H2SO4

21

macromolecular/giant covalent crystal structure

a large number of atoms linked in regular 3D arrangement by covalent bonds e.g. diamond, silicon dioxide

22

giant ionic crystal structure

a lattice of positive ions each surrounded in a regular arrangement by negative ions and vice versa

23

metallic crystal structure

a regular lattice of positively charged metal ions held together by a cloud of negative delocalised electrons

24

properties of ionically bonded compounds (4)

1. solids at room
2. giant structures > high melting temps > energy must be supplied to break up the lattice of ions
3. conduct elect when molten or in solution > ions are free to move
4. brittle and shatter easily when given a sharp blow > lattice of alternating +ve and -ve ions so a blow may move ions and produce contact between ions with like charges

25

properties of covalently bonded compounds (3)

1. gases/liquids/solids with low melting temps > weak attraction between molecules, not much energy needed to move apart
2. poor conductors of elect > neutral molecules so no charged particles to carry current
3. dissolve in water and remain as molecules > no cond of elect in solution bc no charged particles

26

properties of metallic bonded compounds (4)

1. good cond of heat and elect > delocalised electrons & energy spread by increasingly vigorous vibrations of closely packed ions
2. strong > delocalised electrons extend through solid so no indiv bonds to break (dep on charge & size of ion - more e- and closer to nucleus)
3. malleable and ductile (beaten into shape and pulled into thin wires) > after a small distortion, each metal ion is still exactly in the same env as before so new shape is retained
4. high melting points > giant structures > strong attraction between metal ions and delocalised sea of electrons, making atoms diff to separate

27

electronegativity depends on... (3)

1. nuclear charge
2. distance between nucleus and outer e- shell
3. shielding of nuclear charge by inner e-

28

crystals?

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29

shapes of molecules?

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