What is the plum pudding model of the atom?

The plum pudding model is Thomson's model of the atom in which negative electrons are spread throughout a soft, positively charged sphere, like plums in a pudding. It was proposed in 1897 following the discovery of the electron.

What did Rutherford's gold foil experiment show about the structure of the atom?

The experiment showed that most of an atom is empty space and that almost all of its mass is concentrated in a tiny, positive central region called the nucleus . This replaced the plum pudding model with the nuclear model.

True or False? J.J. Thomson discovered the proton in 1897.

False. Thomson discovered the electron in 1897, not the proton. He used a cathode-ray tube to show that electrons are negatively charged subatomic particles.

Bohr proposed that electrons orbit the nucleus in fixed .......... at set .......... from the nucleus.

Bohr proposed that electrons orbit the nucleus in fixed shells at set distances from the nucleus.

Why did Dalton's atomic model have to be revised after Thomson's discovery?

Dalton believed atoms could not be divided into smaller particles. Thomson's discovery of the electron proved that atoms do contain smaller subatomic particles, so the idea that atoms are indivisible had to be abandoned.

What problem with the nuclear model did Bohr's model solve?

The nuclear model did not explain why electrons were not pulled into the positive nucleus . Bohr proposed that electrons occupy fixed shells at set energies, preventing them from collapsing inward.

True or False? In Rutherford's nuclear model, electrons orbit the nucleus in fixed energy shells.

False. Fixed energy shells were proposed by Bohr in 1913, not Rutherford. In Rutherford's nuclear model, electrons simply orbit the nucleus without defined shells.

In science, new experimental .......... may lead to a scientific model being changed or .......... .

In science, new experimental evidence may lead to a scientific model being changed or replaced .

Place these atomic models in chronological order: nuclear model, plum pudding model, Dalton's model, Bohr's model.

The atomic model has changed over time as new evidence emerged:\n\n- Dalton's model : solid sphere (early 1800s)\n- Plum pudding model : sphere of positive charge with embedded electrons (Thomson, 1904)\n- Nuclear model : small positive nucleus with orbiting electrons (Rutherford, 1911)\n- Bohr's model : electrons in fixed energy levels/shells (Bohr, 1913)

Define nucleus (atomic structure).

The nucleus is the central region of an atom containing protons and neutrons . It is extremely small relative to the overall size of the atom but contains virtually all of the atom's mass.

What are the relative masses and charges of a proton, neutron and electron?

The three subatomic particles are:\n\n- Proton : relative mass 1, relative charge +1, found in the nucleus\n- Neutron : relative mass 1, relative charge 0, found in the nucleus\n- Electron : relative mass 1/1836 (negligible), relative charge −1, found in shells around the nucleus

True or False? The radius of the nucleus is roughly equal to the radius of the atom.

False. The nucleus is about 10 000 times smaller than the atom. Most of the atom is empty space occupied by the rapidly moving electrons.

Atoms are extremely small, with a radius of about 1 x 10 -10 .......... .

Atoms are extremely small, with a radius of about 1 x 10 -10 metres .

Why is the mass of an electron described as negligible?

An electron is approximately 1836 times lighter than a proton or neutron. Its mass is so small compared to those particles that it makes a negligible contribution to the overall mass of an atom.

What are shells in atomic structure?

Shells are the orbital paths outside the nucleus in which electrons move. Each shell is at a set distance from the nucleus and has a fixed energy level.

True or False? Protons and neutrons have the same relative mass.

True. Both protons and neutrons are assigned a relative mass of 1. Their masses are very similar so the same value is used for both.

Why is virtually all of an atom's mass concentrated in the nucleus?

The nucleus contains protons and neutrons, each with a relative mass of 1. Electrons have negligible mass and move in the space outside the nucleus, so they contribute almost nothing to the total mass.

Protons and neutrons are located in the .......... of the atom, while electrons move in .......... around it.

Protons and neutrons are located in the nucleus of the atom, while electrons move in shells around it.

Define atomic number .

The atomic number (symbol Z) is the number of protons in the nucleus of an atom. It is unique to each element and also equals the number of electrons in a neutral atom.

How do you calculate the number of neutrons in an atom?

Number of neutrons = mass number (A) - atomic number (Z). For example, beryllium (A = 9, Z = 4) has 9 - 4 = 5 neutrons.

True or False? Isotopes of the same element have different numbers of protons.

False. Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons . Changing the proton number would make it a different element.

The .......... number is the total number of protons and neutrons in the nucleus of an atom.

The mass number is the total number of protons and neutrons in the nucleus of an atom.

Why do isotopes of the same element have the same chemical properties?

Isotopes have the same number of electrons in their outer shells, and it is the outer electrons that determine an element's chemical behaviour . The extra neutrons in one isotope add mass only and do not affect chemistry.

An ion is an atom or group of atoms that carries an electrical charge. It forms when an atom gains or loses electrons, giving it an unequal number of protons and electrons.

An atom of element X has a mass number of 63 and 34 neutrons. How many protons does it have?

Number of protons = mass number - number of neutrons = 63 - 34 = 29 protons . This identifies the element as copper.

True or False? A Mg 2+ ion has fewer electrons than a neutral magnesium atom.

True. A neutral magnesium atom has 12 electrons. The Mg 2+ ion has lost two electrons, so it has only 10 electrons . The number of protons remains 12.

A positive ion is called a .......... and a negative ion is called an .......... .

A positive ion is called a cation and a negative ion is called an anion .

Does the atomic number of magnesium change when it forms a Mg 2+ ion? Explain why.

No. The atomic number does not change because no protons are gained or lost when an ion forms. Only electrons are lost or gained, altering the charge but not the identity of the element.

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Atomic Structure (OCR GCSE Combined Science A (Gateway): Chemistry): Flashcards

Exam code: J250

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What is the plum pudding model of the atom?

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What is the plum pudding model of the atom?
The plum pudding model is Thomson's model of the atom in which negative electrons are spread throughout a soft, positively charged sphere, like plums in a pudding. It was proposed in 1897 following the discovery of the electron.
What did Rutherford's gold foil experiment show about the structure of the atom?
The experiment showed that most of an atom is empty space and that almost all of its mass is concentrated in a tiny, positive central region called the nucleus. This replaced the plum pudding model with the nuclear model.
True or False?
J.J. Thomson discovered the proton in 1897.
False.
Thomson discovered the electron in 1897, not the proton. He used a cathode-ray tube to show that electrons are negatively charged subatomic particles.
Bohr proposed that electrons orbit the nucleus in fixed .......... at set .......... from the nucleus.
Bohr proposed that electrons orbit the nucleus in fixed shells at set distances from the nucleus.
Why did Dalton's atomic model have to be revised after Thomson's discovery?
Dalton believed atoms could not be divided into smaller particles. Thomson's discovery of the electron proved that atoms do contain smaller subatomic particles, so the idea that atoms are indivisible had to be abandoned.
What problem with the nuclear model did Bohr's model solve?
The nuclear model did not explain why electrons were not pulled into the positive nucleus. Bohr proposed that electrons occupy fixed shells at set energies, preventing them from collapsing inward.
True or False?
In Rutherford's nuclear model, electrons orbit the nucleus in fixed energy shells.
False.
Fixed energy shells were proposed by Bohr in 1913, not Rutherford. In Rutherford's nuclear model, electrons simply orbit the nucleus without defined shells.
In science, new experimental .......... may lead to a scientific model being changed or ...........
In science, new experimental evidence may lead to a scientific model being changed or replaced.
Place these atomic models in chronological order: nuclear model, plum pudding model, Dalton's model, Bohr's model.
The atomic model has changed over time as new evidence emerged:\n\n- Dalton's model: solid sphere (early 1800s)\n- Plum pudding model: sphere of positive charge with embedded electrons (Thomson, 1904)\n- Nuclear model: small positive nucleus with orbiting electrons (Rutherford, 1911)\n- Bohr's model: electrons in fixed energy levels/shells (Bohr, 1913)
Define nucleus (atomic structure).
The nucleus is the central region of an atom containing protons and neutrons. It is extremely small relative to the overall size of the atom but contains virtually all of the atom's mass.
What are the relative masses and charges of a proton, neutron and electron?
The three subatomic particles are:\n\n- Proton: relative mass 1, relative charge +1, found in the nucleus\n- Neutron: relative mass 1, relative charge 0, found in the nucleus\n- Electron: relative mass 1/1836 (negligible), relative charge −1, found in shells around the nucleus
True or False?
The radius of the nucleus is roughly equal to the radius of the atom.
False.
The nucleus is about 10 000 times smaller than the atom. Most of the atom is empty space occupied by the rapidly moving electrons.
Atoms are extremely small, with a radius of about 1 x 10^-10 ...........
Atoms are extremely small, with a radius of about 1 x 10^-10 metres.
Why is the mass of an electron described as negligible?
An electron is approximately 1836 times lighter than a proton or neutron. Its mass is so small compared to those particles that it makes a negligible contribution to the overall mass of an atom.
What are shells in atomic structure?
Shells are the orbital paths outside the nucleus in which electrons move. Each shell is at a set distance from the nucleus and has a fixed energy level.
True or False?
Protons and neutrons have the same relative mass.
True.
Both protons and neutrons are assigned a relative mass of 1. Their masses are very similar so the same value is used for both.
Why is virtually all of an atom's mass concentrated in the nucleus?
The nucleus contains protons and neutrons, each with a relative mass of 1. Electrons have negligible mass and move in the space outside the nucleus, so they contribute almost nothing to the total mass.
Protons and neutrons are located in the .......... of the atom, while electrons move in .......... around it.
Protons and neutrons are located in the nucleus of the atom, while electrons move in shells around it.
Define atomic number.
The atomic number (symbol Z) is the number of protons in the nucleus of an atom. It is unique to each element and also equals the number of electrons in a neutral atom.
How do you calculate the number of neutrons in an atom?
Number of neutrons = mass number (A) - atomic number (Z). For example, beryllium (A = 9, Z = 4) has 9 - 4 = 5 neutrons.
True or False?
Isotopes of the same element have different numbers of protons.
False.
Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. Changing the proton number would make it a different element.
The .......... number is the total number of protons and neutrons in the nucleus of an atom.
The mass number is the total number of protons and neutrons in the nucleus of an atom.
Why do isotopes of the same element have the same chemical properties?
Isotopes have the same number of electrons in their outer shells, and it is the outer electrons that determine an element's chemical behaviour. The extra neutrons in one isotope add mass only and do not affect chemistry.
Define ion.
An ion is an atom or group of atoms that carries an electrical charge. It forms when an atom gains or loses electrons, giving it an unequal number of protons and electrons.
An atom of element X has a mass number of 63 and 34 neutrons. How many protons does it have?
Number of protons = mass number - number of neutrons = 63 - 34 = 29 protons. This identifies the element as copper.
True or False?
A Mg²⁺ ion has fewer electrons than a neutral magnesium atom.
True.
A neutral magnesium atom has 12 electrons. The Mg²⁺ ion has lost two electrons, so it has only 10 electrons. The number of protons remains 12.
A positive ion is called a .......... and a negative ion is called an ...........
A positive ion is called a cation and a negative ion is called an anion.
Does the atomic number of magnesium change when it forms a Mg²⁺ ion? Explain why.
No. The atomic number does not change because no protons are gained or lost when an ion forms. Only electrons are lost or gained, altering the charge but not the identity of the element.

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