Atomic Structure (Edexcel GCSE Physics): Flashcards
Exam code: 1PH0
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- FrontInside the Atom
Define nucleus.
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Cards in this collection (50)
Define nucleus.
The nucleus is the tiny, dense, positively charged centre of an atom.
What two particles are found in the nucleus of an atom, and what is the charge of each?
Protons (positive charge) and neutrons (no charge).
What particle orbits the nucleus, and what is its charge?
Electrons, which have a negative charge.
The radius of the nucleus is over ______ times smaller than the radius of the whole atom.
The radius of the nucleus is over 10,000 times smaller than the radius of the whole atom.
How does the mass of an electron compare with the mass of a proton or a neutron?
An electron has about 1/2000 the mass of a proton or a neutron, so its mass is almost negligible.
Define the radius of an atom.
An atom has a radius of about 1 × 10⁻¹⁰ m.
Approximately how many atoms could fit side by side across the width of your thumbnail?
About one hundred million (100,000,000) atoms.
True or False?
The nucleus contains almost all of the mass of an atom.
True.
Almost all of an atom's mass is concentrated in the protons and neutrons of the nucleus, since electrons have almost no mass.
Define relative mass.
A way of comparing the masses of subatomic particles, measured in atomic mass units, where a relative mass of one is equal to 1.67 × 10⁻²⁷ kg.
What are the relative mass and relative charge of a proton?
Relative mass 1, relative charge +1.
What are the relative mass and relative charge of a neutron?
Relative mass 1, relative charge 0 (no charge).
What are the relative mass and relative charge of an electron?
Relative mass almost 0 (negligible), relative charge −1.
Define a positron.
The antiparticle of an electron; it has the same mass as an electron but a positive charge.
A positron can be produced during beta-______ decay, when a proton spontaneously changes into a neutron and a positron.
A positron can be produced during beta-plus decay, when a proton spontaneously changes into a neutron and a positron.
Why is the total charge of a neutral atom always zero?
Because the number of electrons is always equal to the number of protons, so their charges cancel out.
True or False?
An atom that loses electrons becomes negatively charged.
False.
An atom that loses electrons has more protons than electrons, so it becomes positively charged (ionised).
Define atomic number.
The atomic number (or proton number) is the number of protons in an atom; it is unique to each element.
Define mass number.
The mass number (or nucleon number) is the total number of protons and neutrons in the nucleus of an atom.
How can you calculate the number of neutrons in an atom?
Number of neutrons = mass number − atomic number.
Why is the atomic number of an atom always equal to its number of electrons?
Because a neutral atom has no overall charge, so it must have the same number of electrons as protons.
In nuclear notation, the ______ number is written above the element symbol and the ______ number is written below it.
In nuclear notation, the mass number is written above the element symbol and the atomic number is written below it.
Why isn't the number of electrons included in an atom's mass number?
Because electrons have a negligible (tiny) mass compared with protons and neutrons.
True or False?
Two atoms of the same element can have different mass numbers.
True.
Atoms of the same element always have the same atomic number, but the mass number can differ if the number of neutrons differs (isotopes).
Define isotopes.
Isotopes are atoms of the same element with an equal number of protons but a different number of neutrons.
Do isotopes of an element have the same number of protons and electrons?
Yes — isotopes have the same number of protons and electrons; only the number of neutrons differs.
Why does changing the number of neutrons in an atom not affect its chemical properties?
Neutrons have no charge, so they don't affect the atom's charge, only its mass.
Chlorine has an average mass number of 35.5 because it has two isotopes, chlorine-35 and chlorine-______.
Chlorine has an average mass number of 35.5 because it has two isotopes, chlorine-35 and chlorine-37.
Why is chlorine's average mass number closer to 35 than to 37?
Because chlorine-35 is about three times more abundant than chlorine-37.
Define an unstable isotope.
An isotope with an imbalance of protons and neutrons, making its nucleus unstable.
True or False?
Hydrogen has three naturally occurring isotopes.
True.
Hydrogen exists as three isotopes with different numbers of neutrons, though two of them (deuterium and tritium) are far rarer than ordinary hydrogen.
Define energy levels.
The particular distances from the nucleus at which electrons orbit; also called electron shells.
How many electrons can occupy the first and second energy levels of an atom?
The first energy level holds up to two electrons; the second (and third) hold up to eight.
How does an electron's potential energy change as it moves to a higher energy level?
Its potential energy increases, since it is now further from the nucleus.
Where do the colours of the visible light spectrum come from?
They are produced by electrons emitting electromagnetic radiation as they move down to lower energy levels.
When an electron absorbs electromagnetic radiation, it moves to a ______ energy level.
When an electron absorbs electromagnetic radiation, it moves to a higher energy level.
What happens to an electron's energy level when it emits electromagnetic radiation?
It moves down to a lower energy level, closer to the nucleus.
True or False?
Dark coloured objects are good absorbers of electromagnetic radiation.
True.
Dark objects do not reflect much of the radiation that hits them, so they absorb more of it.
Define an ion.
An atom or particle with a non-zero (overall) charge.
Name three ways in which an atom can lose an electron to become an ion.
By friction (rubbing objects together), by absorbing electromagnetic radiation, or through a chemical reaction.
Why does an atom become positively charged when it loses electrons?
Because electrons are negatively charged, so losing them leaves the atom with more protons than electrons.
If a neutral atom loses two electrons, what is the charge of the resulting ion?
+2, calculated as 0 − 2(−1) = +2.
Ions are ______ reactive than neutral atoms because of their charge.
Ions are more reactive than neutral atoms because of their charge.
True or False?
An atom that gains two electrons forms a 2+ ion.
False.
Gaining electrons makes an atom more negatively charged; losing two electrons forms a 2+ ion.
Define model.
A model is a way of describing something in order to explain how it behaves.
Describe the Plum Pudding model of the atom.
The atom consists of negatively charged electrons (the "plums") embedded in a positively charged "pudding", making the atom neutral overall.
State the three observations made in Rutherford's alpha particle scattering experiment.
Most alpha particles passed straight through the gold foil
Some changed direction but continued through the foil
A few bounced back off the foil
In the nuclear model, nearly all of the mass of the atom is concentrated in the ______, which is ______ charged.
In the nuclear model, nearly all of the mass of the atom is concentrated in the nucleus, which is positively charged.
Define energy levels.
Energy levels are the different distances from the nucleus at which electrons orbit, as described in the Bohr model.
Give two reasons why the Bohr model became the accepted model of the atom.
It could explain the absorption and emission of electromagnetic radiation
Theoretical calculations using the model agreed with experimental results
True or False?
The bouncing back of alpha particles in Rutherford's experiment could be explained by the Plum Pudding model.
False.
The bouncing back could not be explained by the Plum Pudding model, so the nuclear model was created to replace it.
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