3.1.1: Periodicity

Question 1

Periods

Answer 1

The rows of the Periodic Table

Question 2

How are the elements of the Periodic Table arranged?

Answer 2

In order of increasing atomic (proton) number
• Rows = periods, show repeating trends in physical and chemical properties.
• Columns = groups, show elements with similar chemical properties because they have similar outer electron shell configuration

Question 3

First ionisation energy

Answer 3

Energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous unipositive cations.

Question 4

First ionisation energy equation

Answer 4

X (g) –> X⁺(g) +e-

Question 5

Factors affecting ionisation energy

Answer 5

• Nuclear charge
• Atomic radius
• Shielding

Question 6

Trend in effective nuclear charge across periodic table

Answer 6

Effective nuclear charge increases L to R
∵ Nuclear charge increases due to increasing no. protons
• Increasing positive charge acts through the same electron shielding
(∴ atomic radius comparatively decreases)

Question 7

Periodicity

Answer 7

Repeating pattern across different periods (rows) in the periodic table.

Question 8

Trend in atomic radii down a group

Answer 8

• Number of quantum shells of e- increases
•.Outermost e- are further from the nucleus
∴ Atomic radii increase down a group
Despite increasing nuclear charge

Question 9

Trend in MBP across a period of transition metals

Answer 9

• MBP increases with valency
∴ MBP increases across a transition metal period
∵ More electrons to donate to ‘sea of electrons’

Question 10

Trend in atomic radii across a period

Answer 10

Decreases across a period
• e- added to same quantum shell of electrons
• Positive charge from nucleus acts through same e- shielding