Periodic Trends

Question 1

Atomic radius : across a period left to right

Answer 1

• across a period left to right, atomic number increases, core charge increases, valence electrons are more strongly attracted to the nucleus and the distance between the valence electrons and nucleus decreases, hence atomic radius slightly decreases

Question 2

Atomic radius : down a group top

Answer 2

• down a group, number of valence electrons remains constant, core charge remains constant but number of electron shells increases, distance between valence electrons and nucleus increases, hence atomic radius increases

Question 3

Atomic radius

Answer 3

the distance between the outermost valence electron and the nucleus

Question 4

Ionisation energy

Answer 4

the minimum amount of energy required to remove an electron in order to form an ion

Question 5

First ionisation energy

Answer 5

the minimum amount of energy required to remove the first valence electron from the outermost shell of an atom

Question 6

Using successive ionisation energy to determine the group of an element

Answer 6

• successive ionisation energy is the consecutive energy required to continuously remove electrons from an atom
• successive ionisation energy shows a large jump after all the valence electrons have been removed as the next electron that must be removed is a shell that is closer and more strongly attracted to the nucleus so a significantly greater amount of energy will be required
• as the number of valence electrons corresponds to the group an element is in, the massive jump can be used to determine the elements group by determining the number of valence electrons it has

Question 7

Effect of core charge on ionisation energy

Answer 7

• as core charge increases, electrons are more strongly attracted to the nucleus, hence more energy is required to overcome the attraction, hence ionisation energy increases
• added egegeggege

Question 8

First ionisation energy: down a group

Answer 8

• down a group, atomic radius increases, valence electrons are less strongly attracted by the nucleus, therefore less energy is required to remove an electron, hence ionisation energy decreases

Question 9

Electronegativity

Answer 9

• the ability of the nucleus to attract electrons

Question 10

Electronegativity: across a period left to right

Answer 10

• left to right across a group, atomic radius decreases, shielding effect is constant, electrons are more strongly attracted to the nucleus, therefore electronegativity increases

Question 11

Electronegativity: down a group

Answer 11

• down a group, atomic radius increases, shielding effect increases, electrons are less strongly attracted to the nucleus, therefore electronegativity decreases

Question 12

Reactivity of metals

Answer 12

• metals react by losing their valence electrons in order to achieve noble gas configuration and become ions
• this is greatest when the ionisation energy is greatest as in order to become ions metals need to lose electrons and ionisation energy refers to the ability of an atom to lose its electrons
• down a group, atomic radius increases, shielding effect increases, valence electrons are more loosely held, therefore ionisation energy increases
• across a period left to right, atomic radius decreases, shielding effect remains constant, electrons are more strongly attracted to the nucleus, therefore ionisation energy decreases
• hence reactivity of elements is increases going down a group and right to left across a period

Question 13

Reactivity of metals

Answer 13

• metals react by losing their valence electrons in order to achieve noble gas configuration and become ions
• this is greatest when the ionisation energy is greatest as in order to become ions metals need to lose electrons and ionisation energy refers to the ability of an atom to lose its electrons
• down a group, atomic radius increases, shielding effect increases, valence electrons are more loosely held, therefore ionisation energy increases
• across a period left to right, atomic radius decreases, shielding effect remains constant, electrons are more strongly attracted to the nucleus, therefore ionisation energy decreases
• hence reactivity of elements increases going down a group and right to left across a period

Question 14

Reactivity of non-metals

Answer 14

• non-metals react by gaining electrons to achieve noble gas configuration and become ions
• this is greatest when the electronegativity is greatest as in order to become ions non-metals need to gain (attract) electrons
• across a period left to right, atomic radius decreases, electrons are more strongly attracted to the nucleus, hence electronegativity increases
• down a group, atomic radius increases, shielding effect increases, electrons are less strongly attracted to the nucleus, hence electronegativity decreases
• hence reactivity of non-metals increases left to right across a period and bottom to top up a group