Chapter 8.1 - Physical Properties Of Period 3 Elements

Question 1

State the element in Period 3 that has the highest melting point. Explain your answer. (3)

Answer 1

• silicon,
• strong covalent bonds present,
• needs lots of energy to break the bonds

Question 2

State the element in Period 3 that has the highest first ionisation energy. Explain your answer. (3)

Answer 2

• argon,
• largest nuclear charge,
• same amount of shielding

Question 3

Suggest the element in Period 3 that has the highest electronegativity value. (1)

Answer 3

-chlorine

Question 4

State what is used to ionise a sample of indium in a mass spectrometer. (1)

Answer 4

-electron gun to knock out electrons

Question 5

State why more than the minimum energy is not used to ionise the sample of indium. (1)

Answer 5

-so no more than 1 electron is knocked out

Question 6

Give two reasons why the sample of indium must be ionized (2)

Answer 6

• acceleration,

- detection

Question 7

State and explain the general trend in first ionisation energies for the Period 3 elements aluminium to argon. (3)

Answer 7

• increases,
• Increase in nuclear charge,
• same shielding

Question 8

Explain why the atomic radius of the elements decrease across Period 3 from sodium to chlorine. (2)

Answer 8

• nuclear charge increases,

- attraction between nucleus and electrons increase

Question 9

Explain why the melting point of sulfur is greater than that of phosphorus (2)

Answer 9

• sulphur molecules are bigger than phosphorus molecules,

- strong van der waals forces between molecules in sulphur

Question 10

Identify the Period 2 element, from carbon to fluorine, that has the largest atomic radius. Explain your answer (3)

Answer 10

• carbon,
• smallest nuclear charge,
• same shielding

Question 11

State the general trend in first ionisation energies from carbon to neon.

Deduce the element that deviates from this trend and explain why this element deviates from the trend.
Trend:
Element:
Explanation (4)

Answer 11

Trend: increases,
Element: oxygen,
Explanation: spin pair repulsion, electrons repel from each other in 2p orbital

Question 12

Explain why the second ionisation energy of carbon is higher than the first ionisation energy of carbon (1)

Answer 12

• electron is being lost from a positive ion,

- more energy needed to remove an electron from a positive ion

Question 13

State the meaning of the term first ionisation energy of an atom (2)

Answer 13

The minimum energy needed to remove 1 mole of electron from 1 mole of an atom in a gaseous state

Question 14

There is a general trend in the first ionisation energies of the Period 3 elements, Na – Ar

(i) State and explain this general trend. (3)

Answer 14

• increases,
• nuclear charge increases,
• same shielding

Question 15

Explain why the first ionisation energy of sulphur is lower than would be predicted from the general trend. (2)

Answer 15

• spin pair repulsion,

- electrons in the 3p orbital repel

Question 16

State the trend in atomic radius from phosphorus to chlorine and explain the trend (3)

Answer 16

• decreases,
• nuclear charge increases,
• same shielding

Question 17

In terms of structure and bonding, explain why sulfur has a higher melting point than phosphorus (3)

Answer 17

• Sulphur molecules larger phosphorus molecules,
• strong van der waals forces between sulphur molecules,
• therefore more energy is required

Question 18

State and explain the trend in electronegativity values across Period 3 from sodium to chlorine. (3)

Answer 18

• increases,
• nuclear charge increases,
• same shielding

Question 19

What is the maximum number of electrons that can be accommodated in an s sub-level? (1)

Answer 19

2

Question 20

Continuation…

What is the maximum number of electrons that can be accommodated in an s sub-level?

Answer 20

-2 elements before the drop in energy to Al

Question 21

This question is about elements in the period 3 from aluminum to argon.

State which element of these elements have the highest electro negativity (1)

Answer 21

Chlorine

Question 22

Explain, in terms of structure and bonding, why the melting point of silicon is greater than the melting point of phosphorus. (4)

Answer 22

• silicon is a giant covalent,
• silicon contains many covalent bonds,
• phosphorus is simple molecular,
• phosphorus has van der waals forces between molecules,
• covalent bonds require much more energy to break than van der waals