1: Atomic Structure and the Periodic Table
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Explain the structure of an atom in terms of electrons, protons and neutrons.
Protons and neutrons contained in the nucleus. Electrons in shells around the nucleus.
Give the relative mass of protons, neutrons and electrons
Proton: 1 Neutron: 1 Electron: 1/1840
Give the relative charge of protons, neutrons and electrons
Proton: +1 Neutron: None Electron: -1
If an atom has an atomic number = Z and a mass number = M, determine the number of each type of sub-atomic particle.
Proton: Z Neutron: M - Z Electron: Z
Explain the term ‘isotopes’.
Atoms with the same atomic number, but different mass numbers.
Define atomic number
The number of protons in the nucleus of an atom
Define mass number
the total number of protons and neutrons in the nucleus of an atom
Define relative isotopic mass
The mass of an atom of a particular isotope of an element, relative to 1/12th the mass of a carbon-12 atom.
Define relative atomic mass
The weighted average mass of all isotopes of an element, relative to 1/12th the mass of a carbon-12 atom.
What is relative molecular mass?
The average mass of a molecule of a substance, relative to 1/12th the mass of a carbon-12 atom.
What is relative formula mass?
The sum of the atomic masses of all the atoms in a particular formula. - Used for compounds with giant structures.
Mass spectrometry What happens in the ionisation stage?
Electrons from the electron gun collide with the particles and form charged ions.
Mass spectrometry What happens in the acceleration stage?
An electric field accelerates the particles to a uniform speed.
Mass spectrometry What happens in the deflection stage?
A magnetic field deflect the particles. Particles with less mass and more charge are deflected more. An electromagnet varies the strength of the field.
Mass spectrometry What happens in the detection stage?
The ions create an electric current which is detected.
Define 1st ionisation energy.
The energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
Define successive ionisation energies.
The energy required to remove 1 electron from each ion in 1 mole of gaseous ions to form 1 mole of gaseous (2+, 3+, 4+, …) ions
How does the number of protons influence ionisation energy?
More protons -> stronger attraction -> higher IE
How does electron shielding influence ionisation energy?
More shielding -> weaker attraction -> lower IE
How does the electron subshell from which the electron is removed influence ionisation energy?
Greater distance -> weaker attraction -> lower IE
State and explain the general trend in first ionisation energy as you go across a period.
Nuclear charge increases, Shielding increases slightly, Atomic radius decreases, Strength of attraction between nucleus and outer electron increases, so first ionisation energy increases.
State and explain the trend in first ionisation energy as you go down a group.
Nuclear charge increases, Shielding increases, Atomic radius increases, Strength of attraction between nucleus and outer electron decreases, so first ionisation energy decreases.
What ideas provide evidence for the existence of quantum shells?
• Atomic emission spectra • Successive ionisation energies • First ionisation energies of successive elements
What do the atomic emission spectra provide evidence for?
The existence of quantum shells.