Particles in the Atom & Atomic Radius (Cambridge (CIE) A Level Chemistry): Exam Questions

The Bohr model of an atom represents a central nucleus, consisting of protons and neutrons, with electrons surrounding it moving in circular orbits. This model was proposed by Niels Bohr in 1913 and after some further research, energy levels and sublevels were recognised, and the model was refined.  

Using your knowledge of atomic structure, complete Table 1.1 below for the particles found in an atom. 

Table 1.1

State the block in the Periodic Table in which silicon is placed. Explain your answer.

A mass spectrometer can be used to detect isotopes of an element, such as silicon. For these to be detected in the mass spectrometer, a sample containing the isotopes must first be vapourised and then ionised.

Give two reasons why the sample of isotopes must be ionised, and state what could be adjusted in order to allow ions formed by different isotopes to reach the detector.

Using your Periodic Table, complete Table 1.1

Table 1.1

Sodium is an element in Period 3. State and explain the trend in atomic radius across the period.

Trend ...........................................................................................................................................

Explanation .................................................................................................................................

Chlorine is an element in Period 3 which has an atomic radius of 99 pm. The chloride ion has an ionic radius of 167 pm.

Explain the difference between the two radii.

The composition of atoms and ions can be determined from knowledge of atomic number, nucleon number and charge.

Complete Table 3.1.

Table 3.1 

Beams of protons, neutrons and electrons behave differently in an electric field due to their differing properties.

Fig. 3.1 shows the path of a beam of electrons in an electric field.

Add and label lines to Fig. 3.1 to represent the paths of beams of electrons and neutrons in the same field.

Fig. 3.1

Chlroine and sulfur are in Period 3. Outline why the chlorine atom has a smaller atomic radius than the sulfur atom.

Table 4.1 below shows the atomic radii for the elements of Period 2, Li to F.

Table 4.1 

i) Explain the variation in atomic radius. 

[4]

 ii) The value for neon is missing in Table 4.1. Explain why the atomic radius of neon cannot be measured in the same way as the other Period 2 elements. 

[2]

Complete Fig. 4.1 to show the electronic configuration of boron in the excited state.

 Fig. 4.1

Explain why the first ionisation energy of boron is lower than the first ionisation of beryllium.

The successive ionisation energies for another element, J, are shown in Table 4.2. 

Table 4.2 

 State the formula of the compound when element J reacts with chlorine.