Lesson test: Periodicity

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Periodicity

1.[2p]
Mendeleev left gaps in his table rather than closing them up. Why does that matter more than the arrangement itself?

A scheme that predicts the properties of unknown elements is a theory, not a catalogue

Correct

It made the table easier to print

The answer is: A scheme that predicts the properties of unknown elements is a theory, not a catalogue

It showed that atomic weights were unreliable

The answer is: A scheme that predicts the properties of unknown elements is a theory, not a catalogue

It allowed later elements to be inserted without renumbering

The answer is: A scheme that predicts the properties of unknown elements is a theory, not a catalogue

2.[2p]
Moseley showed that the ordering variable is atomic number, not atomic weight. Which anomaly did that resolve?

Tellurium is heavier than iodine yet belongs before it

Correct

Hydrogen does not fit any group cleanly

The answer is: Tellurium is heavier than iodine yet belongs before it

The lanthanides all have similar chemistry

The answer is: Tellurium is heavier than iodine yet belongs before it

Argon and neon are both unreactive

The answer is: Tellurium is heavier than iodine yet belongs before it

3.[1p]
Atomic radius falls across a period. What is the reason?

$Z_{eff}$ rises while $n$ stays the same, so the shell is pulled in

Correct

Electrons are removed as you move to the right

The answer is: $Z_{\text{eff}}$ rises while $n$ stays the same, so the shell is pulled in

The nucleus becomes denser

The answer is: $Z_{\text{eff}}$ rises while $n$ stays the same, so the shell is pulled in

Repulsion between electrons decreases

The answer is: $Z_{\text{eff}}$ rises while $n$ stays the same, so the shell is pulled in

4.[2p]
The first ionisation energy of boron (801 kJ per mol) is lower than that of beryllium (899). Why?

Boron's outermost electron is in a $2 p$ orbital, which penetrates the core less and is better shielded

Correct

Boron has a larger nuclear charge

The answer is: Boron's outermost electron is in a $2p$ orbital, which penetrates the core less and is better shielded

Beryllium has a half-filled subshell

The answer is: Boron's outermost electron is in a $2p$ orbital, which penetrates the core less and is better shielded

Boron's electron is paired and suffers extra repulsion

The answer is: Boron's outermost electron is in a $2p$ orbital, which penetrates the core less and is better shielded

5.[2p]
Oxygen (1314 kJ per mol) is easier to ionise than nitrogen (1402). Why?

Oxygen's fourth $2 p$ electron must pair, and pairing costs repulsion energy that is repaid on removal

Correct

Oxygen has a smaller nuclear charge

The answer is: Oxygen's fourth $2p$ electron must pair, and pairing costs repulsion energy that is repaid on removal

Oxygen's electron is in a higher shell

The answer is: Oxygen's fourth $2p$ electron must pair, and pairing costs repulsion energy that is repaid on removal

Nitrogen is more electronegative

The answer is: Oxygen's fourth $2p$ electron must pair, and pairing costs repulsion energy that is repaid on removal

6.[2p]
Put these isoelectronic ions in order of decreasing radius.

F⁻
Na⁺
N³⁻
Mg²⁺

Show the answer

n, f, na, mg

7.[1p]
Fluorine has a more negative electron affinity than chlorine, because it sits higher in the group.

True

The answer is: False

False

Correct

1.[2p] Mendeleev left gaps in his table rather than closing them up. Why does that matter more than the arrangement itself?

2.[2p] Moseley showed that the ordering variable is atomic number, not atomic weight. Which anomaly did that resolve?

3.[1p] Atomic radius falls across a period. What is the reason?

4.[2p] The first ionisation energy of boron (801 kJ per mol) is lower than that of beryllium (899). Why?

5.[2p] Oxygen (1314 kJ per mol) is easier to ionise than nitrogen (1402). Why?

6.[2p] Put these isoelectronic ions in order of decreasing radius.

7.[1p] Fluorine has a more negative electron affinity than chlorine, because it sits higher in the group.

1.[2p]
Mendeleev left gaps in his table rather than closing them up. Why does that matter more than the arrangement itself?

2.[2p]
Moseley showed that the ordering variable is atomic number, not atomic weight. Which anomaly did that resolve?

3.[1p]
Atomic radius falls across a period. What is the reason?

4.[2p]
The first ionisation energy of boron (801 kJ per mol) is lower than that of beryllium (899). Why?

5.[2p]
Oxygen (1314 kJ per mol) is easier to ionise than nitrogen (1402). Why?

6.[2p]
Put these isoelectronic ions in order of decreasing radius.

7.[1p]
Fluorine has a more negative electron affinity than chlorine, because it sits higher in the group.