Atomic Structure - Ionisation Energies

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Questions and Answers

What is ionisation?

When electrons have been removed from an atom or molecule, it's been ionised.

Define the term 'first ionisation energy'.

The first ionisation energy is the energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.

What's the equation for the 1st ionisation energy of oxygen?

O(g) ---> O+(g) + e- (1st ionisation energy = +1314 kJ mol-1)

What are the three important rules about ionisation energies?

<ol> <li>Use the gas state symbol (g) because ionisation energies are measured for gaseous atoms. 2. Always refer to 1 mole of atoms rather than to a single atom. 3. The lower the ionisation energy, the easier it is to form a positive ion.</li> </ol> Signup and view all the answers

How does a higher ionisation energy affect the energy needed to remove the electron from an atom or molecule?

A high ionisation energy means there's a high attraction between the electron and the nucleus, therefore more energy is needed to remove the electron. Signup and view all the answers

What three factors affect ionisation energy?

<ol> <li>Nuclear charge. 2. Distance from nucleus. 3. Shielding.</li> </ol> Signup and view all the answers

How does nuclear charge affect ionisation energy?

The more protons there are in the nucleus, the stronger the attraction for the electrons. Higher nuclear charge = higher ionisation energy. Signup and view all the answers

How does distance from nucleus affect ionisation energy?

Attraction falls very rapidly with distance. Closer to nucleus = higher ionisation energy. Signup and view all the answers

How does shielding affect ionisation energy?

More shielding means outer electrons feel less attraction to the nucleus, resulting in lower ionisation energy. Signup and view all the answers

Why is ionisation always an endothermic process?

Ionisation is always an endothermic process because you have to put in energy to remove an electron from an atom or molecule. Signup and view all the answers

Of lithium and sodium, which has the higher ionisation energy, and why?

Lithium has a higher ionisation energy (+519 kJ mol-1) compared to sodium (+496 kJ mol-1) because sodium's outer electron is further away from the nucleus and experiences a greater shielding effect. Signup and view all the answers

Define the term 'second ionisation energy'.

The second ionisation energy is the energy needed to remove an electron from each ion in 1 mole of gaseous 1+ ions. Signup and view all the answers

What's the equation for the 2nd ionisation energy of oxygen?

O+(g) ---> O2+ + e- (2nd ionisation energy = +3388 kJ mol-1) Signup and view all the answers

Why are second ionisation energies greater than first ionisation energies?

Second ionisation energies are greater than first ionisation energies because the electron is being removed from a positive ion, which requires more energy. Signup and view all the answers

Why is the second ionisation energy of lithium much higher than the first?

The second electron removed is closer to the nucleus and not blocked by any inner electrons, resulting in a stronger nuclear attraction with no shielding. Signup and view all the answers

What is meant by successive ionisation energies?

Successive ionisation energies are the energies required to remove multiple electrons from an atom, one at a time, leaving only the nucleus. Signup and view all the answers

Study Notes

Ionisation Definition

Ionisation involves the removal of electrons from an atom or molecule.

First Ionisation Energy

Energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.

First Ionisation Energy of Oxygen

Equation: O(g) → O+(g) + e-
First ionisation energy = +1314 kJ mol⁻¹.

Important Rules about Ionisation Energies

Utilise the gas state symbol (g) as measurements are for gaseous atoms.
Reference 1 mole of atoms rather than individual atoms.
Lower ionisation energy facilitates easier formation of positive ions.

Impact of High Ionisation Energy

High ionisation energy indicates strong attraction between the electron and the nucleus, requiring more energy for electron removal.

Factors Affecting Ionisation Energy

Nuclear charge: More protons result in higher ionisation energy due to increased attraction.
Distance from nucleus: Electrons closer to the nucleus experience stronger attraction, resulting in higher ionisation energy.
Shielding: Increased number of inner electrons reduces outer electron attraction to the nucleus, impacting ionisation energy.

Nuclear Charge and Ionisation Energy

Higher nuclear charge correlates with higher ionisation energy due to increased positive charge attracting electrons.

Distance from Nucleus and Ionisation Energy

Attraction decreases rapidly with distance; closer electrons have higher ionisation energy due to stronger attraction.

Shielding and Ionisation Energy

Greater shielding from inner electrons leads to less attraction felt by outer electrons, thus increasing ionisation energy.

Endothermic Nature of Ionisation

Ionisation is an endothermic process because energy input is required to remove an electron from an atom or molecule.

Comparison of Ionisation Energies of Lithium and Sodium

Lithium has a higher ionisation energy (+519 kJ mol⁻¹) than sodium (+496 kJ mol⁻¹) due to greater distance and shielding experienced by sodium's outer electron.

Second Ionisation Energy

Energy needed to remove an electron from each ion in 1 mole of gaseous 1+ ions.

Second Ionisation Energy of Oxygen

Equation: O+(g) → O2+ + e-
Second ionisation energy = +3388 kJ mol⁻¹.

Comparison of First and Second Ionisation Energies

Second ionisation energies exceed first ionisation energies because the removal is from a positive ion, requiring more energy.

Second Ionisation Energy of Lithium

Higher due to removal from the first shell (1s²), which is closer to the nucleus and experiences no shielding.

Successive Ionisation Energies

The process includes removing all electrons from an atom, resulting in successive ionisation energies, each corresponding to the removal of an electron.

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Description

Explore the fundamental concepts of ionisation and ionisation energies with this quiz. Test your knowledge on definitions, equations, and specific details regarding atomic structure related to ionisation. Perfect for students studying chemistry.