consecutive ionisation energies

The first ionization energies, in kJ mol–1, of four elements with consecutive atomic
numbers are shown below.
A 1680
B 2080
C 496
D 738

(a) Which element could be an inert gas?
(1)
A
B
C
D
(b) Which element could be X in a covalent compound with formula HX?
(1)
A
B
C
D
(c) Which element could be Y in an ionic compound with formula YH2
A
B
C
D

um sure about the answer for part (a) which is 2080....but um not sure about the others. for (b) as per the mark scheme the answer is 1680...why cant it be D. 738? and for part (c) mark scheme says the ans. is 738....um utterly confused... can someone pls explain this to me with an example of four elements with consecutive atomic numbers. i'd be grateful

Original post by jana668

The first ionization energies, in kJ mol–1, of four elements with consecutive atomic
numbers are shown below.
A 1680
B 2080
C 496
D 738

(a) Which element could be an inert gas?
(1)
A
B
C
D
(b) Which element could be X in a covalent compound with formula HX?
(1)
A
B
C
D
(c) Which element could be Y in an ionic compound with formula YH2
A
B
C
D

um sure about the answer for part (a) which is 2080....but um not sure about the others. for (b) as per the mark scheme the answer is 1680...why cant it be D. 738? and for part (c) mark scheme says the ans. is 738....um utterly confused... can someone pls explain this to me with an example of four elements with consecutive atomic numbers. i'd be grateful

Play around with this interactive - successive ionisations of potassium - (hover over the data points) it may help ...

(edited 10 years ago)

Reply 2

Borek

4

Perhaps you missed the fact these are CONSECUTIVE elements. Once you decided which one is a noble gas, placement of others in the periodic table is obvious, hence their chemical properties are obvious as well.

Reply 3

jana668

OP

1

Original post by Borek

Perhaps you missed the fact these are CONSECUTIVE elements. Once you decided which one is a noble gas, placement of others in the periodic table is obvious, hence their chemical properties are obvious as well.

no i didnt miss it. when i take a look at the periodic table and go from say...neon with ionization energy 2080, the next element is sodium. so its ionization should be lower than neon. my question is why cant it be 738 instead of 1680 for part (b)? both are lower than 2080. and for part (c) i know that it should be a group 2 element. so next to sodium is magnesium. as per the mark scheme, sodium has ionization energy of 1680 and magnesium has 738. but as we go across the period, ionization energy should increase, shouldnt it? and moreover, part (b) says which element forms a "covalent" bond with the formula HX. this is whats confusing me. if we take any consecutive element from any noble gas, its a metal, isnt it? and metals dont form covalent bonds, do they? :confused:

Reply 4

ak96_x

1

do you do Edexcel? I see questions like this in exam papers and I'm confused as to whether we're meant to know the general trend or know the actual figures for the ionisation energies?! (Sorry doesn't answer your question, haven't done the topic fully)

Posted from TSR Mobile

Reply 5

jana668

OP

1

Original post by ak96_x

do you do Edexcel? I see questions like this in exam papers and I'm confused as to whether we're meant to know the general trend or know the actual figures for the ionisation energies?! (Sorry doesn't answer your question, haven't done the topic fully)

Posted from TSR Mobile

yes um doing edexcel A level. and chill we dont need to know the figures. its just a past paper question. knowing the general trend will do good. :wink:

(edited 10 years ago)

Reply 6

Borek

4

Original post by jana668

my question is why cant it be 738 instead of 1680 for part (b)?

What is the bonding in HCl (and analogues)? What is the bonding in NaH (and analogues)?

Reply 7

jana668

OP

1

Original post by Borek

What is the bonding in HCl (and analogues)? What is the bonding in NaH (and analogues)?

um....the bonding is ionic, right? :s-smilie:

(edited 10 years ago)

Reply 8

Borek

4

Which one is ionic? They are different.

Reply 9

JayaRK

3

Original post by jana668

The first ionization energies, in kJ mol–1, of four elements with consecutive atomic
numbers are shown below.
A 1680
B 2080
C 496
D 738

(a) Which element could be an inert gas?
(1)
A
B
C
D
(b) Which element could be X in a covalent compound with formula HX?
(1)
A
B
C
D
(c) Which element could be Y in an ionic compound with formula YH2
A
B
C
D

um sure about the answer for part (a) which is 2080....but um not sure about the others. for (b) as per the mark scheme the answer is 1680...why cant it be D. 738? and for part (c) mark scheme says the ans. is 738....um utterly confused... can someone pls explain this to me with an example of four elements with consecutive atomic numbers. i'd be grateful

After establishing that 2080 is the ionisation energy of an inert gas (noble gas therefore group 8 so, requires the most energy. However, that is option B and as the question says that the ionisation energies given are consecutive, option A is the energy for group 7 and in question B, they ask for a covalent compound whose valency is 1, which means it is present in group 7. Then after 2080, option C is the ionisation energy for Group 1 ( as it comes after--- consecutive-- group 8) which means its valency is also 1. However, for question b, it asked for a covalent Compound, and metals can't form covalent compound. Thus, completely eliminating option c which was in group 1 as mentioned above. Hope it helps : )

Reply 10

Pigster

20

Original post by JayaRK

After establishing that 2080 is the ionisation energy of an inert gas (noble gas therefore group 8 so, requires the most energy. However, that is option B and as the question says that the ionisation energies given are consecutive, option A is the energy for group 7 and in question B, they ask for a covalent compound whose valency is 1, which means it is present in group 7. Then after 2080, option C is the ionisation energy for Group 1 ( as it comes after--- consecutive-- group 8) which means its valency is also 1. However, for question b, it asked for a covalent Compound, and metals can't form covalent compound. Thus, completely eliminating option c which was in group 1 as mentioned above. Hope it helps : )

Hello and welcome to TSR.

When replying to someone, I'd suggest that you first check when the post you are about to reply to was posted.

Six years later, I don't think jana668 will see your reply.