Atomic Structure, Isotopes, and Ionisation Energies: GCSE Chemistry Review

What are the three fundamental particles of an atom?

Proton, neutron, and electron.

What is the relative charge and mass of a proton?

+1 charge and mass of 1.

What is the relative charge and mass of a neutron?

0 charge and mass of 1.

What is the relative charge and mass of an electron?

-1 charge and mass of 1/1840.

How is the atomic number (Z) defined?

The atomic number is the number of protons in the nucleus.

How is the mass number (A) defined?

The mass number is the total number of protons and neutrons in the atom.

How do you calculate the number of neutrons in an atom?

Number of neutrons = A - Z.

What model of the atom was proposed before the discovery of the electron?

Atoms were thought to be tiny spheres that could not be divided.

What is the plum-pudding model of the atom?

A model suggesting that the atom is a ball of positive charge with negative electrons embedded in it.

What did Rutherford's alpha scattering experiments demonstrate?

Most of the mass and positive charge of the atom is concentrated in the nucleus.

What is the nuclear model of the atom?

A model where the center of the atom is called the nucleus, with electrons orbiting around it.

What did Niels Bohr contribute to atomic theory?

He suggested that electrons orbit the nucleus at specific distances and energy levels.

What are isotopes?

Atoms with the same number of protons but different numbers of neutrons.

Why do isotopes have similar chemical properties?

They have the same electronic structure.

What is the purpose of a mass spectrometer?

To determine the isotopes present in a sample of an element and identify elements.

What are the four essential steps in a mass spectrometer?

Ionisation, acceleration, flight tube, and detection.

What is electron impact ionisation?

A technique where high-energy electrons knock out an outer electron from a vaporized sample.

What is electro spray ionisation?

A technique used for larger organic molecules where the sample is dissolved in a solvent and ionized without fragmentation.

What happens during the acceleration step in a mass spectrometer?

Positive ions are accelerated by an electric field to a constant kinetic energy.

How does the velocity of particles relate to their mass in a mass spectrometer?

Lighter particles have a faster velocity, while heavier particles have a slower velocity.

What does the time of flight (t) depend on in a mass spectrometer?

It depends on the distance (d) and the velocity (v) of the particle.

What is detected in the detection step of a mass spectrometer?

The ions generate a current proportional to their abundance, which is analyzed by a computer.

What is the significance of the m/z ratio in mass spectrometry?

It represents the mass-to-charge ratio of ions, allowing identification of isotopes.

How can you calculate the time taken for an ion to travel in a flight tube?

Using the formula t = d/v, where d is the length of the flight tube and v is the velocity.

What is the Avogadro constant?

L = 6.022 × 10^23 mol-1

How do you calculate the mass of one ion of 59Ni+?

Mass of one ion = Mass of one mole of 59Ni / Avogadro constant = 59 / 6.022 × 10^23 = 9.797 × 10^-23 g

What is the mass of one ion of 59Ni+ in kg?

9.797 × 10^-26 kg

What formula is used to calculate time (t) in the given context?

t = 0.8000 √(9.797 × 10^-26 / (2 × 1.000 × 10^-16))

What is the calculated time (t) from the formula?

t = 1.771 × 10^-5 s

What is the relative atomic mass (R.A.M)?

A weighted average of all isotopes of an element.

How do you calculate the R.A.M of magnesium (Mg)?

R.A.M = [(78.7 x 24) + (10.13 x 25) + (11.17 x 26)] / 100 = 24.3

What is the equation for calculating R.A.M using relative abundance?

R.A.M = Σ(isotopic mass x relative abundance) / total relative abundance

How do you calculate the percentage abundance of isotopes?

Use the equation: 63.55 = y x 63 + (1-y) x 65

What is the percentage abundance of 63-Cu?

72.5%

What is the percentage abundance of 65-Cu?

27.5%

What isotopes does chlorine (Cl) have and their abundances?

Cl35 (75%) and Cl37 (25%)

What isotopes does bromine (Br) have and their abundances?

Br79 (50%) and Br81 (50%)

What is the significance of the peak in a mass spectrum?

The peak with the largest m/z corresponds to the complete molecule and is equal to the relative molecular mass (Mr) of the molecule.

What happens to the mass peak in electro spray ionisation?

The peak equals the mass of the MH+ ion, requiring subtraction of 1 to find the relative molecular mass.

What is the Bohr model of the atom?

An early model with electrons in spherical orbits, predicting stability for atoms with noble gas configurations.

What are the sub-levels in atomic structure?

s, p, d, and f with specific electron capacities: s (2), p (6), d (10), f (14).

What is the order of filling sub-shells in atomic structure?

1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p

How does electronic structure change for negative ions?

Electrons are gained, e.g., O2- becomes 1s2 2s2 2p6.

How does electronic structure change for positive ions?

Electrons are lost from the outermost shell, e.g., Mg2+ becomes 1s2 2s2 2p6.

What is the electronic structure of d-block elements?

4s fills before 3d, but some elements like chromium and copper have unusual arrangements.

What unusual electronic structure do chromium and copper have?

They have a half-filled 4s subshell.

When d-block elements form ions, which electrons do they lose first?

They lose the 4s electrons before the 3d electrons.

What is the definition of first ionization energy?

The enthalpy change when one mole of gaseous atoms forms one mole of gaseous ions with a single positive charge.

What is the equation representing first ionization energy?

H(g) → H⁺(g) + e⁻

What is the definition of second ionization energy?

The enthalpy change when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge.

What is the equation representing second ionization energy?

Ti⁺(g) → Ti²⁺(g) + e⁻

What are the three main factors that affect ionization energy?

1. Attraction of the nucleus, 2. Distance of electrons from the nucleus, 3. Shielding of the nucleus' attraction.

Why are successive ionization energies always larger?

The removal of the first electron creates a positive ion, increasing the attraction on the remaining electrons.

What does a big jump in ionization energy indicate?

It indicates that an electron is being removed from a shell closer to the nucleus with less shielding.

Why does helium have the largest first ionization energy?

Helium's first electron is in the first shell closest to the nucleus with no shielding effects from inner shells.

Why do first ionization energies decrease down a group?

Outer electrons are further from the nucleus and more shielded, reducing the attraction from the nucleus.

Why is there a general increase in first ionization energy across a period?

Electrons are added to the same shell, increasing the number of protons and thus the effective nuclear attraction.

Why does sodium have a lower first ionization energy than neon?

Sodium's outer electron is in a 3s shell further from the nucleus and more shielded, making it easier to remove.

What causes the small drop in ionization energy from magnesium to aluminum?

Aluminum starts to fill a 3p subshell, making its outer electrons slightly easier to remove due to higher energy and shielding.

What causes the small drop in ionization energy from phosphorus to sulfur?

Sulfur has four electrons in the 3p subshell, and the addition of the second electron creates slight repulsion, making it easier to remove.

What is periodicity in the context of ionization energy?

A repeating pattern across a period that provides useful information about electronic structure.

What happens to the second ionization energy graph compared to the first?

The second ionization energy graph shifts one position to the left compared to the first ionization energy graph.

Why does lithium have a high second ionization energy?

Lithium's second electron is removed from the first 1s shell closest to the nucleus with no shielding effects.

What is the significance of the big jump between successive ionization energies?

It indicates a transition to removing electrons from a more stable, inner shell.