Physical properties of period 3 elements-
mark-scheme answers
State the element in Period 3 that has the highest melting point. Explain your answer.
(3) - Correct Answer Silicon - giant covalent so has many strong covalent bonds that
must be broken
State the element in Period 3 that has the highest first ionization energy. Explain your
answer.
(3) - Correct Answer Argon - largest number of protons/largest nuclear charge. Same
amount of shielding.
Give two reasons why the sample of In must be ionized
(2) - Correct Answer Reason 1- acceleration
Reason 2- deflection
State and explain the difference, if any, between the chemical properties of the isotopes
113In and 115In
(2) - Correct Answer None
Because they both have the same number of electrons in the outer shell.
State and explain the general trend in first ionization energy across Period 3.
(3) - Correct Answer General increase
Greater nuclear charge / more protons
Same shielding / electrons added to same shell
Stronger attraction (from nucleus) for outer electron(s)
There is a similar general trend in first ionization energies for the Period 4 elements
gallium to krypton. State how selenium deviates from this general trend and explain
your answer.
(3) - Correct Answer Lower
Paired electrons in a (4) p orbital
(Paired electrons) repel
Suggest why the first ionization energy of krypton is lower than the first ionization
energy of argon. - Correct Answer Kr is a bigger atom / has more shells / more
shielding in Kr / electron removed further from nucleus/ electron removed from a higher
(principal or main) energy level
mark-scheme answers
State the element in Period 3 that has the highest melting point. Explain your answer.
(3) - Correct Answer Silicon - giant covalent so has many strong covalent bonds that
must be broken
State the element in Period 3 that has the highest first ionization energy. Explain your
answer.
(3) - Correct Answer Argon - largest number of protons/largest nuclear charge. Same
amount of shielding.
Give two reasons why the sample of In must be ionized
(2) - Correct Answer Reason 1- acceleration
Reason 2- deflection
State and explain the difference, if any, between the chemical properties of the isotopes
113In and 115In
(2) - Correct Answer None
Because they both have the same number of electrons in the outer shell.
State and explain the general trend in first ionization energy across Period 3.
(3) - Correct Answer General increase
Greater nuclear charge / more protons
Same shielding / electrons added to same shell
Stronger attraction (from nucleus) for outer electron(s)
There is a similar general trend in first ionization energies for the Period 4 elements
gallium to krypton. State how selenium deviates from this general trend and explain
your answer.
(3) - Correct Answer Lower
Paired electrons in a (4) p orbital
(Paired electrons) repel
Suggest why the first ionization energy of krypton is lower than the first ionization
energy of argon. - Correct Answer Kr is a bigger atom / has more shells / more
shielding in Kr / electron removed further from nucleus/ electron removed from a higher
(principal or main) energy level
