3.2 Variation Of Properties Down A Group And Across A Period

Question 1

What is electronegativity?

Answer 1

The attraction of an atom for the electron pair in the covalent bond of which it is a part.

Question 2

How does electronegativity change down a group?

Answer 2

Decreases.

Question 3

How does electronegativity change across a period?

Answer 3

Increases.

Question 4

What is atomic radius?

Answer 4

Radius of an atom.

Question 5

How does atomic radius change down a group?

Answer 5

Increases.

Question 6

How does atomic radius change across a period?

Answer 6

Decreases.

Question 7

What is ionic radius?

Answer 7

Radius of an ion.

Question 8

How does ionic radius change down a group?

Answer 8

Increases.

Question 9

How does ionic radius change across a period?

Answer 9

Decreases for positive ions as charge gets higher, increases for negative ions as charge gets higher.

Question 10

What is ionisation energy?

Answer 10

Energy required to remove an electron from a gaseous atom - M(g) —> M+(g) + e-

Question 11

How does ionisation energy change down a group?

Answer 11

Decreases.

Question 12

How does ionisation energy change across a period?

Answer 12

Increases (beware of exceptions).

Question 13

What is electron affinity?

Answer 13

The energy given out when an electron is added to a gaseous atom - M(g) + e- —> M-(g)

Question 14

How does electron affinity change down a group?

Answer 14

Decrease becomes less exothermic (beware of exceptions).

Question 15

How does electron affinity change across a period?

Answer 15

Increases becomes more exothermic (beware of exceptions not a clear trend).

Question 16

How can the trends down a group be explained?

Answer 16

Down a group there are more shells of electrons so the atoms get bigger this means the outer electrons are further from the nucleus and less strongly attracted.

Question 17

How can trends across a period be explained?

Answer 17

Across a period there is an increase in the number of protons in the nucleus with no significant increase in shielding therefore the attraction of the nucleus for the outer electrons increases.

Question 18

Why are the noble gases not included in any trends?

Answer 18

Because they are inert and do not generally form compounds.

Question 19

Why are the radii of positive ions smaller than their atomic radii?

Answer 19

M and M+ have the same number of protons therefore the same amount of nuclear attraction.
M+ has one fewer electron therefore less electron electron repulsion so the electrons are pulled in more closely and the size is smaller.

Question 20

Why are the radii of negative ions larger than their atomic radii?

Answer 20

Same number of protons so the nuclear attraction is the same, X- has one more electron so there is greater electron electron repulsion.

Question 21

Why does the electron affinity become less exothermic from Cl to I?

Answer 21

As the size of the atom increases the electron is brought into the outer shell of the atom and as the atom gets bigger there is a weaker attraction between he added electron and the nucleus as it is brought to a position that is further from the nucleus.

Question 22

What is the decrease in electron affinity between F and Cl due to?

Answer 22

A decrease in electron electron repulsion as the size of the atom/ion increases.

Question 23

What does a metallic structure consist of?

Answer 23

A regular lattice of positive ions in a sea of delocalised electrons.

Question 24

What must an element have to form a metallic structure?

Answer 24

Must be able to lose electrons fairly readily to form positive ions, and have a low ionisation energy.

Question 25

Why are metallic structures less likely to be formed by elements on the right hand side of the periodic table?

Answer 25

Since ionisation energy increase across a period.

Question 26

Why are elements lower down a group more likely to exhibit metallic behaviour?

Answer 26

Since down a group ionisation energy decreases.

Question 27

What is a basic oxide?

Answer 27

One that will react with an acid to form a salt and if soluble in water will produce an alkaline solution.

Question 28

What is an amphoteric oxide?

Answer 28

One that reacts with both acids and bases.

Question 29

What is an acidic oxide?

Answer 29

One that reacts with bases/alkalis to form a salt and if soluble in water will produce an acidic solution.

Question 30

How do the nature of oxides change across a period?

Answer 30

From basic from amphoteric to acidic across a period.

Question 31

What is the equation for Na2O reacting with water?

Answer 31

Na2O(s) + H2O(l) ----> 2NaOH (aq)

Question 32

What is the equation for MgO reacting with water?

Answer 32

MgO(s) + H2O(l) ----> Mg(OH)2(aq)

Question 33

What is the equation for P4010 reacting with water?

Answer 33

P4010(s) + 6H2O(l) ----> 4H2PO4(aq)

Question 34

What is the equation for NO2 reacting with water?

Answer 34

2NO2(g) + H2O(l) ----> HNO2(aq) + HNO3(aq)

Question 35

What is the equation for SO2 reacting with water?

Answer 35

SO2(g) + H2O(l) ----> H2SO3(aq)

Question 36

What is the equation for SO3 reacting with water?

Answer 36

SO3(g) + H2O(l) -----> H2SO4(aq)

Question 37

What do nitrogen and sulfur oxides contribute to?

Answer 37

Acid deposition which can cause damage to trees and kill fish in lakes.