1.3.1 - Periodicity

Question 1

In the Periodic table, the elements are arranged in order of their ______ _____. Each horizontal row is called a _____. Elements across a period shows trends that repeat along every period. This repeating pattern of trends is called _____. Each vertical column is called a _____. They contain elements with similar _____.

Answer 1

In the Periodic table, the elements are arranged in order of their atomic number. Each horizontal row is called a period. Elements across a period shows trends that repeat along every period. This repeating pattern of trends is called periodicity. Each vertical column is called a group. They contain elements with similar properties.

Question 2

Explain how elements in the same group have similar properties.

Answer 2

• Chemical reaction involve electrons in the outer shell.
• Because elements in the same group have similarities in outer shell electron configurations, they will have similar properties.

Question 3

State the three things that affect the ionisation energy of an element.

Answer 3

• Nuclear charge.
• Distance from the nucleus / atomic radius.
• Electron shielding.

Question 4

Describe and explain the pattern of the first ionisation energies of elements across a period.

Answer 4

• Describe - The first ionisation energies of elements across a period generally increase.
• Explain - This is because a proton is being added across each element therefore increasing the nuclear charge.
• Electrons are also being added each time. This draws the outer shell electrons inwards slightly, due to the nuclear attraction. This decreases the atomic radius.
• This means more energy is required to remove an electron from the outer shell.

Question 5

Describe and explain the trend of the first ionisation energies of elements down a group.

Answer 5

• Describe - The first ionisation energies of elements decrease as you go down the group.
• Explain - This is because, a new shell of outer electrons are added as you go down the group. This increases the atomic radius, which decreases the nuclear attraction.
• More shells also mean that the electron shielding increases, resulting in less attraction.
• The number of protons also increase, but this attraction is outweighed by the increase in distance and shielding.

Question 6

Describe the trend in the boiling points of Period 2 and 3 elements from this graph:

Answer 6

• Period 2:
• Li→C : shows a general increase in boiling points.
• C→N : shows a sharp decrease.
• N→F : shows comparatively low boiling points.
• Period 3:
• Na→Si : shows a general increase in boiling points.
• Si→P : shows a sharp decrease.
• P→Ar : shows comparatively low boiling points.

Question 7

Here is a graph of boiling points across elements in Period 2 and 3.

Explain why there is an increase from Na to Al.

Answer 7

• Na to Mg are metals. They have metallic bonds and therefore have a giant metallic structure.
• From Na to Al, there is an increase in protons and electrons in each atom, so the attraction between the ions within the structure increase.
• This means more energy is required to break these strong metallic bonds apart.

Question 8

Explain why the boiling point of carbon is much higher than that of nitrogen.

Answer 8

• There are covalent bonds between carbon atoms in a giant covalent structure. These covalent bonds are very strong and require more energy to break them apart.
• N₂ has weak van der Waals’ forces between its molecules and they have a simple molecular structure. This means less energy is needed to break these weak forces apart.