2.1- ionic model

Question 1

cations

Answer 1

when metal atoms lose electrons, positive ions

Question 2

anions

Answer 2

when non metal atoms gain electrons they form negative ions

Question 3

ionic bonding

Answer 3

electrostatic attraction between oppositely charged ions

Question 4

ionic compounds

Answer 4

exist as 3D lattice structures

Question 5

ammonium

Answer 5

NH4+

Question 6

hydroxide

Answer 6

OH-

Question 7

Nitrate

Answer 7

NO3-

Question 8

Hydrogencarbonate

Answer 8

HCO3-

Question 9

carbonate

Answer 9

CO3 2-

Question 10

sulfate

Answer 10

SO4 2-

Question 11

Phosphate

Answer 11

PO4 3-

Question 12

binary ionic compounds

Answer 12

compunds with two elements
named with cation first followed by anion
anion adopts the suffix “ide” eg magnesium sulfide or sodium oxide

Question 13

lattice enthalpy

Answer 13

measure of the strength of the ionic bond in different compounds

Question 14

why will atoms bond together

Answer 14

to achieve a decrease in their potential energy, lower energetic state is more stable, in practice this is achieved by atoms gaining a full outer shell
3 major types of electronic interaction are possible, resulting in 3 different bonding, what type occurs depends on electronegativity difference of atoms interacting

Question 15

ionic

Answer 15

low electronegativity atoms (metals) interacting with high electronegativity atoms (non-metals)
electronegativity difference bigger than 1.7 units

Question 16

covalent

Answer 16

both atoms have middle to high electronegativity (both non-metals)
electornegativity difference less than 1.7 units

Question 17

metalic

Answer 17

both atoms have low electronegativity (both metals)

Question 18

ionic compounds structure and properties

Answer 18

giant ionic

-solid insulator
-melt/ dissolve conduct
-brittle
-high melting point
-hard some are soluble

Question 19

covalent compounds structure and properties

Answer 19

simple covalent

giant covalent macromolecules

simple covalent:
weak intermolecular forces, low melting points, weak, brittle, non- conducters

giant covalent:
high melting point, non conducter (except graphite), insoluble

Question 20

describe how ionic bonding takes place

Answer 20

metal loses electrons to form a positive ion (cation), oxidation
non metal will gain electrons to form a negative ion (anion), reduction
in both cases atoms achieve the same electronic configuration as nobel gases. This is called ISOELECTRONIC

Question 21

oxidation formula

Answer 21

M -> Mn+ + ne-
n= a number

Question 22

reduction formula

Answer 22

X + ne- -> Xn-

Question 23

what happens once the ions are formed (process of ionic bonding)

Answer 23

electrostatic force of attraction between oppositely charged ions causes them to pack together into a 3d Giant ionic lattice with every cation surrounded by anions and vis versa

the electrostatic attraction, between ions is the ionic bond

Question 24

describe size of cation and anion

Answer 24

as cation has been formed through loss of outermost energy level the cations are smaller than metal atoms
as anion has formed by the gain of electrons they are bigger than the neutral atom, due to increase in electron electron repulsion and expansion of the outer energy level, in general the cation is smaller than the anion

Question 25

transition metals have

Answer 25

variable oxidation states and hence can have variable charges

Question 26

conduction in ionic susbtances

Answer 26

conduct electricity when molten or in a solution, as ions are free to move around and can pass to the elctrodes dipped in solution to become oxidised or reduced (electrolysis)

Question 27

melting point ionic substances

Answer 27

high, as large number of ionic bonds must be broken to allow the ions to move around or break free from the attractive forces completely (ionic gas) ions held together by strong electrostatic forces of attraction

Question 28

softness or hardness and maleability or brittle ionic susbtances

Answer 28

hard and brittle, ionci lattice does not bend, once sufficinet force is applied the structure gives away completely and material snaps strong electrostatic attraction between oppositely charged ions

Question 29

solubility ionic substances

Answer 29

more soluble in polar solvnts that have an uneven charge distribution (such as water) than non polar solvents (eg. hexane). The ions become surrounded by the polar solvent molecules and are dissolve (hydrated in case of water) polar water molecules surround the ions and free them into solution, seperates between hydrated negative and positive ions

Question 30

what is the strength of an ionic lattice measured by

Answer 30

lattice enthalpy, which is the energy recquired to break up a mole of an ionic lattice into gaseous ions under standar conditions

Question 31

define lattice enthalpy

Answer 31

enthalpy change when one mole of solid ionic compound is seperated into its gaseous ions, this wold give the enthalpy change as endothermic (positive)

Question 32

magnitude of the lattice enthalpy is a measure of

Answer 32

stability of the ionic lattice,

Question 33

what two factors affect the stability of the ionic lattice

Answer 33

the size of ions- the smaller ions the more closely the ions can pack together and attract each other the charge on the ions- the more charged is the ion the stronger is the elctrostatic force of attraction between them

Question 34

lattice enthalpy formula

Answer 34

charge on cation X charge on anion/ sum of ionic radii

Question 35

what is lattice enthalpy porpotional to and inversely porportional to

Answer 35

porportional- charge on cation X charge on anion inversely- sum of ionic radii