1.1 Atomic Structure

2 marks

Bromine exists as two stable isotopes. The two isotopes are represented by the symbols ${}_{35}^{79}{Br}$ and ${}_{35}^{81}{Br}$ .

Give one similarity and one difference between these two isotopes by referring to the number of particles in the nuclei of the two isotopes.

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1b3 marks

The relative abundance of the two isotopes in a sample cannot be found in a chemical test.

Give the reason why, despite the difference in atomic structure, the isotopes have the same chemical reactions.

(1)

ii)

State how the relative abundance of the two isotopes can be found.

(2)

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1c2 marks

Complete the electronic configuration of a bromine atom.

(1)

1s² 2s² ...........................................................................................

ii)

What is the number of electrons in the fourth quantum shell of bromine?

(1)

☐	A	2
☐	B	7
☐	C	17
☐	D	18

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1a4 marks

This question is about chlorine.

Chlorine has two isotopes with mass numbers 35 and 37.

Complete the table to show the numbers of subatomic particles in a ³⁵Cl atom and a ³⁷Cl⁻ion.

(2)

Particle	Protons	Neutrons	Electrons
³⁵Cl atom
³⁷Cl⁻ ion

ii)

A sample of chlorine contained 75% of ³⁵Cl and 25% of ³⁷Cl.

Complete the mass spectrum to show the peaks you would expect for the molecular ion

C l_{2}^{+}

from this sample of chlorine gas.

(2)

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1b1 mark

Write the formula of potassium chlorate(V).

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1c2 marks

Write the equation for the first electron affinity of chlorine. Include state symbols.

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1d2 marks

The standard electrode potential for the chlorine / chloride ion half-cell is

1⁄2Cl₂ (aq) + e⁻ ⇌ Cl⁻ (aq)

E_{cell}^{⦵}

= +1.36 V

Identify an oxidising agent from the Data Booklet that will convert chloride ions into chlorine under standard conditions.

(1)

ii)

Calculate the value of

E_{cell}^{⦵}

for the reaction in (d)(i).

(1)

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Isotope	Relative isotopic mass	Percentage abundance
bromine-79	78.918	50.52
bromine-81	80.916	49.48

Region	Maximum number of electrons
the 1s orbital
the 2p subshell
the third quantum shell

Isotope	Relative isotopic mass	Abundance %
³⁹K	38.9637	93.218
⁴⁰K	39.9340	0.012
⁴¹K	40.9618	6.770

Edexcel A Level Chemistry

Topic Questions

1.1 Atomic Structure

☐	A	N^3– and Cl^–
☐	B	O^2– and S^2–
☐	C	Na⁺ and K⁺
☐	D	Na⁺ and Mg²⁺

☐	A	the weighted mean mass of an atom of an element relative to one twelfth of the mass of an atom of the isotope carbon-12
☐	B	the mass of one atom of an isotope relative to one twelfth of the mass of an atom of the isotope carbon-12
☐	C	the weighted mean mass of an atom of an element relative to 12g of the isotope carbon-12
☐	D	the mass of one atom of an isotope relative to the mass of 12g of the isotope carbon-12

☐	A	8 protons, 10 neutrons and 8 electrons
☐	B	9 protons, 9 neutrons and 9 electrons
☐	C	10 protons, 8 neutrons and 10 electrons
☐	D	18 protons, 18 neutrons and 18 electrons