Topic 1: Atomic Structure and the Periodic Table
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Describe the structure of an atom in terms of electrons, protons and neutrons
Atoms contain a positive nucleus with protons and neutrons. they are surrounded by electrons in quantum shells.
Describe the relative mass and relative charge of protons, neutrons and electrons
Proton: mass 1, charge 1+ Neutron: mass 1, no charge Electron: mass 0.0005, charge -1
what is meant by the terms ‘atomic (proton) number’ and ‘mass number’
Atomic number is the number of protons (or the number of electrons). Atomic mass is the number of protons + the number of neutrons.
what are isotopes?
atoms of the same element with the same proton number, but with a different number of neutrons.
define the terms ‘relative isotopic mass’
RELATIVE ISOTOPIC MASS: mass of an atom of an isotope relative to 12th of C-12. its the same as the mass number.
what do electronic configurations determine?
the chemical properties of an element
How do you analyse and interpret data from mass spectrometry to calculate relative atomic mass from relative abundance of isotopes?
the x axis should have the masses. the peaks should show the relative abundance. take the abundance and masses and find the Ar for the element
How can you predict the mass spectra, including relative peak heights, for diatomic molecules, including chlorine?
Diatomic molecules don’t just have peaks at their relative masses- they also have peaks where 2 Cls might be bonded together. For example, there should be a peak at mass 70 or another peak at 72. These are responsible for those peaks: (Cl-37—Cl-35)+ and (Cl-35—Cl-35)+
define the terms ‘first ionisation energy’ and ‘successive ionisation energies’
1st Ionisation energy: energy needed to remove 1M of electrons from 1M of gaseous atoms to form 1M of unipositive gaseous ions. Second ionisation energy: enthalpy to remove one mole of electrons from one mole of uni positive ions to form one mole of 2+ gaseous ions.
How are ionisation energies influenced by the number of protons, and the electron shielding?
More protons= increased nuclear charge, so the electron is more attracted to the nucleus and is harder to remove. Electrons within shells experience repulsion, known as shielding, which makes the electron easier to remove.
Explain reasons for the general increase in first ionisation energy across a period
the number of protons increases, so nuclear charge increases. Increased nuclear charge means greater attraction between the electrons and the nucleus. Electrons are in the same shell, so shielding is the same.
Explain reasons for the decrease in first ionisation energy down a group
Atomic radius increases because of more shells. The outermost electron is further from the nucleus, so the nuclear attraction decreases. More shielding down a group
Write an equation for the first ionisation energy of magnesium
Mg(g) → Mg+(g) + e
Write an equation to show the second ionisation energy if magnesium is being measured
Mg+(g) - e- ———> Mg2+(g)
Explain why the second ionisation energy of an element is always greater than the first ionisation energy
The 2nd electron is closer to the nucleus. The electron is being removed from a positive ion. Therefore there is increased attraction between the e and the nucleus, so more energy is needed to remove it.
Why does first ionisation energy decrease between group 2 to 3 ?
Decreases between 2 to 3 because in group 3 the outermost electrons are in p orbitals. Whereas in group 2 they are in s orbital, so the electrons are harder to remove.
Why does first ionisation energy decrease between group 5 to 6?
group 5 electrons in the p orbital are single electrons. In group 6 the outermost electrons are spin paired, with some repulsion. Therefore the electrons are slightly easier to remove.
Does first ionisation increase or decrease between the end of one period and the start of next? Why?
Decrease There is increase in atomic radius because of more shells. The outermost electron is further from the nucleus, so the nuclear attraction decreases. Increase in electron shielding
Does first ionisation increase or decrease down a group? Why?
Atomic radius increases because of more shells. The outermost electron is further from the nucleus, so the nuclear attraction decreases. More shielding down a group, causing weaker attraction. Increase in number of protons is outweighed by increase in distance and shielding
Explain the structure and bonding for sodium
Giant structure, metallic bonding
why does melting point generally increase across a period?
Proton number increases. The force of attraction between the nucleus and the electrons increases. The ions decrease in size. This attraction needs more energy to overcome.
Give the definition ‘relative atomic mass’, based on the 12C scale
Ar: Average mass of mole of atoms of an element in its natural abundance relative to a 12th of C-12
How many electrons can the 1st, 2nd, 3rd and 4th shell hold?
2,8,18,32
Give the shape of an s-orbital and a p-orbital
the s orbital is a sphere the p orbital has a dumbbell shape