Unit 2: Section 1 - Periodicity

Question 1

How is the periodic table arranged?

Answer 1

Into periods (rows) and groups (columns).

Question 2

All the elements within a period have…

Answer 2

…the same number of electron shells.

Question 3

All the elements within a group have…

Answer 3

…the same number of electrons in their outer shell.

Question 4

Elements with the same valence electronic configuration have…

Answer 4

…similar chemical properties.

Question 5

What does the group number tell you? What is the exception?

Answer 5

The valence electons/the number of electrons in the outer shell.
Group 0, which has a full outer shell.

Question 6

What does the period number tell you?

Answer 6

The number of electron shells.

Question 7

What is atomic/proton number?

Answer 7

The number of protons and electons.

Question 8

What is the mass number?

Answer 8

The number one of protons and neutrons.

Question 9

How are atomic and mass number arranged beside on element in the periodic table?

Answer 9

Mass number on top, atomic number on bottom.

Question 10

What are electron sub-shells?

Answer 10

s, d, p, f

Question 11

Where is the s block in the periodic table?

Answer 11

Group 1 and 2

Question 12

Where is the d block in the periodic table?

Answer 12

Metals

Question 13

Where is the p block in the periodic table?

Answer 13

Groups 3 to 0

Question 14

Where is the f block in the periodic table?

Answer 14

Lanthanides and actinides

Question 15

What are the trends across a period? (5)

Answer 15

• Atomic radius decreases
• Nuclear charge increases
• Ionisation energy increases (generally)
• Shielding remains the same
• Attraction between the nucleus and the valence electrons increases

Question 16

Why does melting point vary across a period?

Answer 16

They depend on the structure of the elements and the bonding within them.

Question 17

Describe the melting points of period 3 elements.

Answer 17

Silicon has the highest, followed by aluminium and magnesium, sodium, sulfur, phosphorus, chlorine and argon, with the lowest.

Question 18

Explain the melting points of sodium, magnesium and aluminium.

Answer 18

Sodium, magnesium and aluminium are metals. Melting point increases for metals as the strength of the metallic bonds increases across the period. This is because the metal ions have an increasing positive charge and number of delocalised electrons and a decreasing atomic radius.

Question 19

Explain the melting point of silicon.

Answer 19

Silicon has a high melting point as it is macromolecular so it is linked by strong covalent bonds. A lot of energy is needed to break these.

Question 20

Explain the melting points of phosphorus, silicon and chlorine.

Answer 20

Phosphorus, sulfur and chlorine are molecular substances. The melting points depend upon the strength of the van der Waals forces between the molecules. Van der Waals forces are weak so they have low melting points. However sulfur has the most atoms of these three so it has a higher melting point than phosphorus and silicon.

Question 21

Explain the melting point of argon.

Answer 21

Argon has a very low melting point because it’s monoatomic, resulting in very weak van der Waals forces.

Question 22

What does monoatomic mean?

Answer 22

It exists as individual atoms.

Question 23

What does diatomic mean?

Answer 23

It exists as a pair of atoms.