Topic 3: Periodicity

Question 1

3 Principle Properties

Answer 1

• Distance from nucleus
• Effective nuclear charge
• Shielding effect

Question 2

Atomic Radius

Answer 2

• Increases down a group (more electrons = bigger, more shielding)
• Decreases across a period (more protons = more attraction)
• Cations smaller than neutral, anions larger than neutral

Question 3

Ionization Energy

Answer 3

• Energy required to remove one electron from a gaseous atom
• Increase across a period (more attraction = more difficult)
• Decreases down a group (electrons further from nucleus)

Question 4

4 Points in an Ionization Energy Graph

Answer 4

• General increase
• Peaks
• Troughs
• Small dips

Question 5

General Increase (IE Graph)

Answer 5

Higher effective nuclear charge = higher attraction and harder to take away an electron

Question 6

Peaks (IE Graph)

Answer 6

The element is stable and an electron is being taken from a full shell so requires a lot of energy

Question 7

Troughs (IE Graph)

Answer 7

Only one electron in the valence shell, so it is easy to remove from the S sub shell to become stable

Question 8

Small Dips (IE Graph)

Answer 8

• Energy is dropping due to the only being one electron in the p sub shell, so the element can have a full s sub shell which is more stable
• Losing an electron will allow for a half full sub shell which is more stable so less energy is required

Question 9

Electron Affinity

Answer 9

• The change in energy when one mole of an electron is added to one mole of gaseous atoms
• EA is generally negative because there is a release of potential energy as heat
• Increases negatively across a period (increasing attraction)
• Decreases down the group (weaker electrostatic energy)

Question 10

Electronegativity

Answer 10

• A measure of the attraction an atom has for a shared electron
• Increases across a period
• Decreases down a group

Question 11

Electronegativity and Type of Bonds

Answer 11

• Calculate the difference between the elements
• less than 0.4, non polar covalent
• 0.4 to 1.7, polar covalent
• more than 1.7, ionic

Question 12

Electronegativity and Type of Bonds

Answer 12

• Calculate the difference between the elements
• less than 0.4, non polar covalent
• 0.4 to 1.7, polar covalent
• more than 1.7, ionic

Question 13

Melting Point

Answer 13

• The stronger the bond the more energy needed to break the bond thus a higher melting point
• Noble gasses have the lowers MP (weak interatomic force)

Question 14

Types of Bonding and Structure

Answer 14

• Ionic, ionic lattice (high MP)
• Covalent, simple molecular (low MP) and giant covalent (high MP)
• Metallic, metallic (relatively high MP but varies)

Question 15

Metallic Characters

Answer 15

• How easily an atom can lose electrons
• Decreases across a period
• Increases down a group