CHEMISTRY 7405 PAPER 3 ACTUAL TEST PAPER
2026 COMPLETE QUESTIONS AND ANSWERS
GRADED A+
◉ Protons. Answer: have a relative charge of +1 and a relative mass
of 1
◉ Neutrons. Answer: have a relative charge of 0 and a relative mass
of 1
◉ Electrons. Answer: have a relative charge of -1 and a relative mass
of 1/1840
◉ Atomic Number. Answer: *The number of protons in an atom. An
atom will have the same number of electrons*
◉ Mass number. Answer: *The number of protons and neutrons in
an atom*
◉ Isotope. Answer: *Atoms of the same element with different
masses due to differing numbers of neutrons*
,◉ Relative atomic mass. Answer: *The weighted mean mass of an
atom of an element compared to the mass of one-twelfth of an atom
of carbon¹²*
◉ Relative Isotopic Mass. Answer: *The mass of an atom of an
isotope of an element compared to one twelfth the mass of an atom
of carbon¹²*
◉ Relative Molecular Mass and Relative Formula Mass. Answer:
Relative molecular mass is the mass of a molecule, relative formula
mass is used for ions (or compounds with giant structures)
◉ Calculating relative molecular mass. Answer: Add up the masses
multiplied by their frequency and then divide the answer by the
total frequency
◉ Mass Spectra. Answer: Mass Spectra will show the masses and
how frequently they occur, either as a number of a percentage. This
can be used to calculate the relative atomic mass of an element.
Diatomic molecules such as chlorine have 3 large peaks at the end
due to the 3 possible combinations of isotopes.
The mass spectrum of a molecule ends in a large molecular ion peak
that gives the relative molecular mass for the molecule
,◉ First ionisation energy. Answer: *The energy required to remove
one mole of ions from one mole of gaseous atoms to form one mole
of unipositive atoms*
◉ Second ionisation energy. Answer: *The amount of energy
required to remove one mole of electrons from one mole of
unipositive ions to form one mole of 2+ ions*
◉ Trends in ionisation energies. Answer: Ionisation energy
decreases down the group as although the nuclear charge increases
(thereby attracting the electrons more) there are more quantum
shells shielding the outer electron from the nucleus and the outer
electron is further from the nucleus, thus inhabiting a higher energy
quantum shell
◉ Subshells. Answer: Quantum shells are made up of subshells.
There are s, p and d subshells
◉ Orbitals. Answer: orbitals make up subshells, each one can
contain 2 electrons
◉ s subshell. Answer: Shaped like a sphere with one orbital (hence
contains 2 electrons)
, ◉ p subshell. Answer: Shaped like 3 dumbbells at right angles to
each other. Has 3 orbitals and thus 6 electrons
◉ d subshell. Answer: Has 5 orbitals and thus 10 electrons
◉ Electron configuration. Answer: This determines an elements
chemical properties
◉ Hund's rule. Answer: Electrons will occupy the orbitals singly
before pairing takes place
◉ Aufbau Principle. Answer: Electrons will fill lower energy
subshells first (hence they fill 4s subshell before the 3 subshell)
◉ Pauli exclusion principle. Answer: For electrons to occupy the
same orbital they must have an opposite spin
◉ Exceptions to electron configuration. Answer: Chromium and
Copper are exceptions to the pattern. This is because for both cases
the 3d subshell is either one electron away from being half full or
completely full. As these states are more stable they pull an electron
down from the 4s subshell.
2026 COMPLETE QUESTIONS AND ANSWERS
GRADED A+
◉ Protons. Answer: have a relative charge of +1 and a relative mass
of 1
◉ Neutrons. Answer: have a relative charge of 0 and a relative mass
of 1
◉ Electrons. Answer: have a relative charge of -1 and a relative mass
of 1/1840
◉ Atomic Number. Answer: *The number of protons in an atom. An
atom will have the same number of electrons*
◉ Mass number. Answer: *The number of protons and neutrons in
an atom*
◉ Isotope. Answer: *Atoms of the same element with different
masses due to differing numbers of neutrons*
,◉ Relative atomic mass. Answer: *The weighted mean mass of an
atom of an element compared to the mass of one-twelfth of an atom
of carbon¹²*
◉ Relative Isotopic Mass. Answer: *The mass of an atom of an
isotope of an element compared to one twelfth the mass of an atom
of carbon¹²*
◉ Relative Molecular Mass and Relative Formula Mass. Answer:
Relative molecular mass is the mass of a molecule, relative formula
mass is used for ions (or compounds with giant structures)
◉ Calculating relative molecular mass. Answer: Add up the masses
multiplied by their frequency and then divide the answer by the
total frequency
◉ Mass Spectra. Answer: Mass Spectra will show the masses and
how frequently they occur, either as a number of a percentage. This
can be used to calculate the relative atomic mass of an element.
Diatomic molecules such as chlorine have 3 large peaks at the end
due to the 3 possible combinations of isotopes.
The mass spectrum of a molecule ends in a large molecular ion peak
that gives the relative molecular mass for the molecule
,◉ First ionisation energy. Answer: *The energy required to remove
one mole of ions from one mole of gaseous atoms to form one mole
of unipositive atoms*
◉ Second ionisation energy. Answer: *The amount of energy
required to remove one mole of electrons from one mole of
unipositive ions to form one mole of 2+ ions*
◉ Trends in ionisation energies. Answer: Ionisation energy
decreases down the group as although the nuclear charge increases
(thereby attracting the electrons more) there are more quantum
shells shielding the outer electron from the nucleus and the outer
electron is further from the nucleus, thus inhabiting a higher energy
quantum shell
◉ Subshells. Answer: Quantum shells are made up of subshells.
There are s, p and d subshells
◉ Orbitals. Answer: orbitals make up subshells, each one can
contain 2 electrons
◉ s subshell. Answer: Shaped like a sphere with one orbital (hence
contains 2 electrons)
, ◉ p subshell. Answer: Shaped like 3 dumbbells at right angles to
each other. Has 3 orbitals and thus 6 electrons
◉ d subshell. Answer: Has 5 orbitals and thus 10 electrons
◉ Electron configuration. Answer: This determines an elements
chemical properties
◉ Hund's rule. Answer: Electrons will occupy the orbitals singly
before pairing takes place
◉ Aufbau Principle. Answer: Electrons will fill lower energy
subshells first (hence they fill 4s subshell before the 3 subshell)
◉ Pauli exclusion principle. Answer: For electrons to occupy the
same orbital they must have an opposite spin
◉ Exceptions to electron configuration. Answer: Chromium and
Copper are exceptions to the pattern. This is because for both cases
the 3d subshell is either one electron away from being half full or
completely full. As these states are more stable they pull an electron
down from the 4s subshell.
