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CAIE A-Level Chemistry AS 1.3 Electrons Energy Levels and Atomic Orbitals Questions

Practise building ground-state electron configurations from shells, sub-shell energies, orbitals and electron-repulsion rules.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • distinguish shells, sub-shells and orbitals and state the electron capacity of each relevant sub-shell
  • fill orbitals in increasing energy while applying opposite spin and single occupancy before pairing
  • determine atom and ion configurations, including transition-element loss of 4s electrons before 3d electrons

Covered syllabus points

1.3.0—Scope note1.3.1—Terms1.3.2—Number of orbitals making up s, p and d1.3.3—Order of increasing energy of the sub-shells1.3.4—Electronic configurations to include1.3.5—Electronic configurations1.3.6—Determine the electronic configuration1.3.7—The electrons in boxes notation1.3.8—And sketch the shapes of s and p orbitals1.3.9—Free radical as a species with one or more

Question 1

[Maximum number: 3]

Vanadium, niobium and tantalum are metals in the same group of the Periodic Table.

Question (a)

(a)

The shorthand electronic configuration of vanadium in the ground state is [Ar]3 d34 s2[\mathrm{Ar}] 3 \mathrm{~d}^{3} 4 \mathrm{~s}^{2}.

[ 3 ]

Question (i)

(i)

State what is meant by the term ground state.

[ 1 ]

Question (ii)

(ii)

Show the electronic configuration of vanadium using electrons in boxes notation.

Figure for Question (ii) — CAIE A-Level Chemistry AS
[ 1 ]

Question (iii)

(iii)

Deduce the total number of electrons in the p sub-shells of a vanadium atom.

[ 1 ]

Question 2

[Maximum number: 6]

Atoms contain the subatomic particles electrons, protons and neutrons. Protons and electrons were discovered by observations of their behaviours in electric fields.

Question (a)

(a)

Electrons in atoms up to 36Kr{ }_{36} \mathrm{Kr} are distributed in s, p and dorbitals.

[ 6 ]

Question (i)

(i)

State the number of occupied orbitals in an isolated atom of 36Kr{ }_{36} \mathrm{Kr}.

Table for Question (i) — CAIE A-Level Chemistry AS
[ 3 ]

Question (ii)

(ii)

Complete the diagram to show the number and relative energies of the electrons in an isolated atom of 14Si{ }_{14} \mathrm{Si}.

Figure for Question (ii) — CAIE A-Level Chemistry AS
[ 2 ]

Question (iii)

(iii)

The diagram shows a type of orbital.

Figure for Question (iii) — CAIE A-Level Chemistry AS

State the total number of electrons that exist in all orbitals of this type in an atom of 9 F{ }_{9} \mathrm{~F}.

[ 1 ]

Question 3

[Maximum number: 5]

Question (a)

(a)

The electronic configuration of a sulfur atom is 1s22s22p63s23p41 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{4}.

[ 4 ]

Question (i)

(i)

Identify which orbital in a sulfur atom has the lowest energy.

[ 1 ]

Question (ii)

(ii)

Sketch the shape of a p orbital.

[ 1 ]

Question (iii)

(iii)

During the process of ionisation a sulfur atom loses an electron.

S( g)→S+(g)+e−ΔH=1000 kJ mol−1\mathrm{S}(\mathrm{~g}) \rightarrow \mathrm{S}^{+}(\mathrm{g})+\mathrm{e}^{-} \quad \Delta H=1000 \mathrm{~kJ} \mathrm{~mol}^{-1}

Identify the orbital from which this electron is removed. Explain your answer.
orbital
explanation

[ 2 ]

Question (b)

(b)

Complete the diagram to show the arrangement of electrons within the third shell of a phosphorus atom.

3s

3s

Figure for Question (b) — CAIE A-Level Chemistry AS
3p

3p

Figure for Question (b) — CAIE A-Level Chemistry AS
[ 1 ]
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