Edexcel A level chemistry paper 1 topics
questions and answers
Atoms - Made up of 3 subatomic particles - electrons, neutrons and protons
Electrons - - Subatomic particle
- Charge of -1
- Arranged in orbitals
- Relative mass of 0.0005 - negligible
Nucleus - - Where most of the mass of the atom is contained
- Made up of protons and neutrons
- Diameter is much smaller than that of whole atom
Neutrons - - Subatomic particle
- No charge
- Relative mass of 1
- Contained in nucleus
- Dictates the isotope of an element that an atom is; not all atoms of the same
element have the same number of neutrons
Protons - - Subatomic particle
,Edexcel A level chemistry paper 1 topics
questions and answers
- Charge of +1
- Relative mass of 1
- Contained in nucleus
- Dictates the type of element that an atom is; all atoms of the same element have
the same number of protons
Ions - - Ions are charged atoms; positive ions have more protons than electrons,
and vice versa for negative ions
- Ions have different numbers of electrons to their parent elements'
- e.g. Li⁺ has only 2 electrons, whereas Li has 3
- e.g. F has 9 electrons, F⁻ has 10
Isotopes - - Isotopes of an element are atoms with the same number of protons
but a different number of neutrons.
- E.g. ³⁵Cl has 18 neutrons and ³⁷Cl has 20
- Number and arrangement of electrons dictate the chemical properties of an
element, so all isotopes of an element have the same chemical properties
- However isotopes of the same element can have different physical properties
such as density and diffusion rates
,Edexcel A level chemistry paper 1 topics
questions and answers
Relative atomic mass - The relative atomic mass is the weighted mean mass of an
atom of an element compared to 1/12th of the mass of an atom of carbon-12
Can be worked out from Isotopic Abundances - Multiply the isotopic mass of each
isotope by its % abundance, add them up then divide the total by 100
Relative isotopic mass - The mass of an atom of an isotope of an element
compared with 1/12th if the mass of an atom of carbon-12
Relative molecular/formula mass - The average mass of a molecule compared to
the mass of an atom of carbon-12
Mass Spectrometry - Can be used to work out the relative atomic mass. Particles
measured with a mass spectrometer must be charged, so they are often
bombarded with electrons in order to remove one, giving a charge of +1
1. Multiply each relative isotopic mass by its relative isotopic abundance, and add
up the results
2. Divide by the sum of the isotopic abundances
, Edexcel A level chemistry paper 1 topics
questions and answers
Calculating Isotopic Masses from Relative atomic mass - Need: Relative mass of
element and all but one of the abundances and isotopic masses of its isotopes
1. Find abundance of last isotope; percentage abundances so do 100-(sum of
known% abundances)
2. Put into equation for finding the relative atomic mass and rearrange for the
unknown value
Predicting mass spectra for diatomic molecules (E.g. Cl₂) - 1. Express each % as a
decimal (e.g. 75%→0.75 and 25%→0.25)
2. Make a table showing all the different Cl₂ molecules. For each, multiply the
abundances of each isotope to get the relative abundance of each molecule.
3. Look for any values in the table that are the same and add up their abundances
4. Divide all the relative abundances by the smallest relative abundance to get the
smallest whole number ratio. And by working out the relative molecular mass of
each molecule, you can predict the mass spectra
5. Plot the mass spectra with the relative abundances you worked out on the y-
axis and the relative molecular masses (m/z) on the x-axis
questions and answers
Atoms - Made up of 3 subatomic particles - electrons, neutrons and protons
Electrons - - Subatomic particle
- Charge of -1
- Arranged in orbitals
- Relative mass of 0.0005 - negligible
Nucleus - - Where most of the mass of the atom is contained
- Made up of protons and neutrons
- Diameter is much smaller than that of whole atom
Neutrons - - Subatomic particle
- No charge
- Relative mass of 1
- Contained in nucleus
- Dictates the isotope of an element that an atom is; not all atoms of the same
element have the same number of neutrons
Protons - - Subatomic particle
,Edexcel A level chemistry paper 1 topics
questions and answers
- Charge of +1
- Relative mass of 1
- Contained in nucleus
- Dictates the type of element that an atom is; all atoms of the same element have
the same number of protons
Ions - - Ions are charged atoms; positive ions have more protons than electrons,
and vice versa for negative ions
- Ions have different numbers of electrons to their parent elements'
- e.g. Li⁺ has only 2 electrons, whereas Li has 3
- e.g. F has 9 electrons, F⁻ has 10
Isotopes - - Isotopes of an element are atoms with the same number of protons
but a different number of neutrons.
- E.g. ³⁵Cl has 18 neutrons and ³⁷Cl has 20
- Number and arrangement of electrons dictate the chemical properties of an
element, so all isotopes of an element have the same chemical properties
- However isotopes of the same element can have different physical properties
such as density and diffusion rates
,Edexcel A level chemistry paper 1 topics
questions and answers
Relative atomic mass - The relative atomic mass is the weighted mean mass of an
atom of an element compared to 1/12th of the mass of an atom of carbon-12
Can be worked out from Isotopic Abundances - Multiply the isotopic mass of each
isotope by its % abundance, add them up then divide the total by 100
Relative isotopic mass - The mass of an atom of an isotope of an element
compared with 1/12th if the mass of an atom of carbon-12
Relative molecular/formula mass - The average mass of a molecule compared to
the mass of an atom of carbon-12
Mass Spectrometry - Can be used to work out the relative atomic mass. Particles
measured with a mass spectrometer must be charged, so they are often
bombarded with electrons in order to remove one, giving a charge of +1
1. Multiply each relative isotopic mass by its relative isotopic abundance, and add
up the results
2. Divide by the sum of the isotopic abundances
, Edexcel A level chemistry paper 1 topics
questions and answers
Calculating Isotopic Masses from Relative atomic mass - Need: Relative mass of
element and all but one of the abundances and isotopic masses of its isotopes
1. Find abundance of last isotope; percentage abundances so do 100-(sum of
known% abundances)
2. Put into equation for finding the relative atomic mass and rearrange for the
unknown value
Predicting mass spectra for diatomic molecules (E.g. Cl₂) - 1. Express each % as a
decimal (e.g. 75%→0.75 and 25%→0.25)
2. Make a table showing all the different Cl₂ molecules. For each, multiply the
abundances of each isotope to get the relative abundance of each molecule.
3. Look for any values in the table that are the same and add up their abundances
4. Divide all the relative abundances by the smallest relative abundance to get the
smallest whole number ratio. And by working out the relative molecular mass of
each molecule, you can predict the mass spectra
5. Plot the mass spectra with the relative abundances you worked out on the y-
axis and the relative molecular masses (m/z) on the x-axis
