AQA CHEMISTRY AS-LEVEL Topic 1
:Physical chemistry
What were the main ideas of Dalton's and Thomson's atomic models?
What did Rutherford's gold foil experiment reveal about the atom?
How did Rutherford's nuclear model lead to the discovery of protons and neutrons?
How did Bohr improve Rutherford's atomic model, and what new concept did he introduce?
How was Bohr's model further refined, and why is it still useful today? - ANS-Dalton proposed
that atoms are indivisible, solid spheres, with different spheres for different elements. Thomson
later discovered electrons, leading to the 'plum pudding' model where electrons were embedded
in a positively charged 'pudding' so atom having no overall charge.
The nuclear atom showcased that atoms are mostly empty space with a tiny, dense, positively
charged nucleus at the center which deflected the alpha particles when it was shot at gold foil.
Rutherford discovered protons after Moseley's research on nuclear charge, and later, James
Chadwick discovered neutrons to explain the additional mass in the nucleus.
Bohr introduced specific energy levels or shells for electrons, explaining why they don't collapse
into the nucleus. His model also accounted for the emission and absorption of light by atoms.
Bohr's model was refined by introducing subshells, helping to explain electron behavior in
bonding and ionization energy.
What are protons, neutrons, and electrons, and where are they located in an atom?
What are the relative masses and charges of subatomic particles?A:
What is the mass number (A) and atomic number (Z)?
What are ions and how do they form?
How do you determine the number of protons, electrons, and neutrons in an ion?
What are the atomic number, protons, electrons, and neutrons in a 37Li+37Li+ ion?
What is the strong nuclear force? - ANS-Protons and neutrons, collectively called nucleons, are
in the nucleus, while electrons orbit in energy shells around the nucleus.
Proton: Relative mass = 1, Charge = +1
Neutron: Relative mass = 1, Charge = 0
Electron: Relative mass = 0.0005, Charge = -1
Mass number (A) is the total number of protons and neutrons in the nucleus.
Atomic number (Z) is the number of protons and also the number of electrons in a neutral atom.
, Ions are atoms that gain or lose electrons, leading to an overall charge. Anions have more
electrons than protons (negative charge), while cations have fewer electrons than protons
(positive charge).
Protons = atomic number
Electrons = atomic number - charge (for cations) or + charge (for anions)
Neutrons = mass number - atomic number
Atomic number (Z) = 3
Protons = 3
Electrons = 2 (since it is a Li+Li+ ion)
Neutrons = 4 (Mass number 7 - Atomic number 3)
The strong nuclear force holds protons and neutrons together in the nucleus, overcoming the
repulsion between positively charged protons. It acts over very short distances and is much
stronger than the electrostatic attraction that holds electrons and protons together in the atom.
What are the main energy shells and their electron capacities?
What is an electron cloud and what are its shapes for s and p orbitals?Draw the orbitals out
What is the filling order of electron orbitals?
How do electrons occupy orbitals within sub-shells?
How is short electron configuration represented using noble gas notation? - ANS-Shell 1 (n=1):
1s orbital holds 2 electrons.
Shell 2 (n=2): 2s (2 electrons) + 2p (6 electrons) = 8 electrons total.
Shell 3 (n=3): 3s (2 electrons) + 3p (6 electrons) + 3d (10 electrons) = 18 electrons total.
Shell 4 (n=4): 4s (2 electrons) + 4p (6 electrons) + 4d (10 electrons) + 4f (14 electrons) = 32
electrons total.Note: Higher shells have electrons with higher energy.
An electron cloud is an area around the nucleus where electrons are likely to be found. It has
dense areas where electrons are more concentrated, like crowded spaces in a room.
s-Orbital: Spherical shape; the cloud is evenly spread around the nucleus.
p-Orbital: Dumbbell shape; the cloud has two lobes on either side of the nucleus with less
density in between.
The order is generally based on increasing energy, but 4s is filled before 3d, and electrons are
removed from 4s before 3d when forming ions.
Electrons will occupy individual orbitals if available and the relationship between 2 electrons in
the same orbitals in term of their spin have opposite spins due to their negative charge repelling
each other.This repulsion makes it easier to remove one of the paired electrons.
It uses square brackets for the preceding noble gas. For example, calcium's configuration is
written as [Ar] 4s².
:Physical chemistry
What were the main ideas of Dalton's and Thomson's atomic models?
What did Rutherford's gold foil experiment reveal about the atom?
How did Rutherford's nuclear model lead to the discovery of protons and neutrons?
How did Bohr improve Rutherford's atomic model, and what new concept did he introduce?
How was Bohr's model further refined, and why is it still useful today? - ANS-Dalton proposed
that atoms are indivisible, solid spheres, with different spheres for different elements. Thomson
later discovered electrons, leading to the 'plum pudding' model where electrons were embedded
in a positively charged 'pudding' so atom having no overall charge.
The nuclear atom showcased that atoms are mostly empty space with a tiny, dense, positively
charged nucleus at the center which deflected the alpha particles when it was shot at gold foil.
Rutherford discovered protons after Moseley's research on nuclear charge, and later, James
Chadwick discovered neutrons to explain the additional mass in the nucleus.
Bohr introduced specific energy levels or shells for electrons, explaining why they don't collapse
into the nucleus. His model also accounted for the emission and absorption of light by atoms.
Bohr's model was refined by introducing subshells, helping to explain electron behavior in
bonding and ionization energy.
What are protons, neutrons, and electrons, and where are they located in an atom?
What are the relative masses and charges of subatomic particles?A:
What is the mass number (A) and atomic number (Z)?
What are ions and how do they form?
How do you determine the number of protons, electrons, and neutrons in an ion?
What are the atomic number, protons, electrons, and neutrons in a 37Li+37Li+ ion?
What is the strong nuclear force? - ANS-Protons and neutrons, collectively called nucleons, are
in the nucleus, while electrons orbit in energy shells around the nucleus.
Proton: Relative mass = 1, Charge = +1
Neutron: Relative mass = 1, Charge = 0
Electron: Relative mass = 0.0005, Charge = -1
Mass number (A) is the total number of protons and neutrons in the nucleus.
Atomic number (Z) is the number of protons and also the number of electrons in a neutral atom.
, Ions are atoms that gain or lose electrons, leading to an overall charge. Anions have more
electrons than protons (negative charge), while cations have fewer electrons than protons
(positive charge).
Protons = atomic number
Electrons = atomic number - charge (for cations) or + charge (for anions)
Neutrons = mass number - atomic number
Atomic number (Z) = 3
Protons = 3
Electrons = 2 (since it is a Li+Li+ ion)
Neutrons = 4 (Mass number 7 - Atomic number 3)
The strong nuclear force holds protons and neutrons together in the nucleus, overcoming the
repulsion between positively charged protons. It acts over very short distances and is much
stronger than the electrostatic attraction that holds electrons and protons together in the atom.
What are the main energy shells and their electron capacities?
What is an electron cloud and what are its shapes for s and p orbitals?Draw the orbitals out
What is the filling order of electron orbitals?
How do electrons occupy orbitals within sub-shells?
How is short electron configuration represented using noble gas notation? - ANS-Shell 1 (n=1):
1s orbital holds 2 electrons.
Shell 2 (n=2): 2s (2 electrons) + 2p (6 electrons) = 8 electrons total.
Shell 3 (n=3): 3s (2 electrons) + 3p (6 electrons) + 3d (10 electrons) = 18 electrons total.
Shell 4 (n=4): 4s (2 electrons) + 4p (6 electrons) + 4d (10 electrons) + 4f (14 electrons) = 32
electrons total.Note: Higher shells have electrons with higher energy.
An electron cloud is an area around the nucleus where electrons are likely to be found. It has
dense areas where electrons are more concentrated, like crowded spaces in a room.
s-Orbital: Spherical shape; the cloud is evenly spread around the nucleus.
p-Orbital: Dumbbell shape; the cloud has two lobes on either side of the nucleus with less
density in between.
The order is generally based on increasing energy, but 4s is filled before 3d, and electrons are
removed from 4s before 3d when forming ions.
Electrons will occupy individual orbitals if available and the relationship between 2 electrons in
the same orbitals in term of their spin have opposite spins due to their negative charge repelling
each other.This repulsion makes it easier to remove one of the paired electrons.
It uses square brackets for the preceding noble gas. For example, calcium's configuration is
written as [Ar] 4s².
