Periodicity

Question 1

What are the elements sat between the dividing line between metals and non-metals called? What properties do they have?

Answer 1

Metalloids, a combination of metal and non-metal properties

Question 2

What is the trend of atomic radius down a group?

Answer 2

Increase in principle energy levels, therefore increase in shielding, outer electron is further from the nucleus.

Question 3

What is the trend of atomic radius across a period?

Answer 3

Decreases as number of protons (nuclear charge) increases, shielding stays constant, electrons are more strongly attracted to the nucleus and atomic radius decreases.

Question 4

What does periodicity mean?

Answer 4

• Repeating trends of physical or chemical properties

Question 5

What is ionisation?

Answer 5

Involves the loss of an electron to form a positive ion

Question 6

Give the definition of the First Ionisation Energy

Answer 6

• The energy required to remove of 1 mol of electrons from 1 mol of gaseous atoms

Question 7

What is the trend of the 1st IE down a group?

Answer 7

Decreases, electron is removed from a higher principle energy level, electron is further from the nucleus, more shielding, weaker attraction between nucleus and outer electron

Question 8

What is the trend of the 1st IE across a period?

Answer 8

Increases, number of protons increase, shielding is constant/ atomic radius decreases, stronger attraction between nucleus and outer electron.

Question 9

What are the two anomalies of the general trend of the 1st IE across period 3? Explain why.

Answer 9

Al and S
Al - IE decreases, electron is removed from a higher energy p sub-level, weaker attraction between nucleus and outer electron
S - IE decreases, pair of electrons in a p-orbital, extra repulsion means less energy required to remove outer electron

Question 10

Explain successive ionisation energies and explain what they can be used for

Answer 10

• Will always increase, positive charge on ion increases, ionic radius decreases, nuclear attraction on the outer electron increases
• Can be used to find an element’s group number (look for the big jump)
• The big jump happens when an electron has been removed from a principle energy level that is much closer to the nucleus

Question 11

Give the definition of metallic bonding

Answer 11

Strong electrostatic force of attraction between positive ions and delocalised electrons

Question 12

Why does a lattice form in metallic bonding?

Answer 12

• Positive ions repel
• Sea of electrons attracted to positive ions

Question 13

Give the 3 factors that determine the strength of metallic bonding

Answer 13

1. Ionic charge on metal - stronger=stronger bond
2. Number of delocalised electrons - more electrons donated to sea the stronger metallic bond
3. Atomic radius - smaller=stronger

Question 14

What are the 3 properties of metals?

Answer 14

1. Good conductors of electricity and heat as delocalised electrons are free to move
2. Very high m.p and b.p as they have a strong attraction between positive ions and delocalised electrons
3. Malleable and ductile (can be hammered into shape) - Layers of ions that can slide over each other

Question 15

Give the bonding and structure of the Period 2 elements

Answer 15

• Lithium and Beryllium - metallic bonding - forms a metallic lattice
• Carbon - covalent bonding to form giant covalent substance; diamond, graphite or graphene - high m.p and b.p, strong covalent bonds require a lot of energy to break
• N2, O2, F2, Ne - non polar molecules, covalent bonding. All have weak London forces

Question 16

Describe the 3 giant covalent substances that carbon forms

Answer 16

• Diamond - each carbon atom bonded to four other carbon atoms, no delocalised electrons
• Graphite - each carbon atom bonded to three other carbon atoms, forming hexagonal layers. Weak London forces between layers, delocalised electrons
• Graphene - 1 layer of graphite, delocalised electrons

Question 17

Give the bonding and structure of period 3 elements

Answer 17

• Na, Mg, Al - metallic bonding - metallic lattice
• Si, giant covalent substance. Each silicon atom bonded to 4 other silicon atoms. Strong covalent bonds require a lot of energy to break. No delocalised electrons
• P4, S8, Cl2, Ar - All non polar, weak London forces require little energy to break

Question 18

Explain what melting point is

Answer 18

1. Some of the attractive forces between the particles are broken. Now move more freely around each other but are still close together
2. The stronger the forces, the more difficult it is to melt

Question 19

Explain what boiling point is

Answer 19

1. All the attractive forces between the particles are broken. Free to move more randomly