The atom

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Lesson notes

Scientific Models

A scientific model is a simplified version of an object or phenomenon, making it easier to understand while still representing key features.
The particle model is one example; it explains and predicts the behaviour of solids, liquids and gases.
Models are changed and updated over time as new evidence emerges.

Dalton Model of the Atom

The Dalton model described atoms as indivisible – they could not be broken down into anything smaller.
This was the earlier model before sub-atomic particles were discovered.

Current Model of the Atom

The atom is made of three sub-atomic particles: protons, neutrons and electrons.
Protons have a positive charge and are found in the nucleus.
Neutrons are neutral (no charge) and also in the nucleus.
Electrons have a negative charge and orbit around the nucleus.
Most of the atom's mass is in the nucleus; protons and neutrons have about 2000 times more mass than an electron.
Overall, an atom is neutral because it has equal numbers of protons and electrons.

Peer Review

Peer review is when other scientists examine new evidence to decide if it is valid.
It prevents incorrect models and theories from being spread.
After peer review, research can be published and other scientists may try to reproduce the results to check repeatability.

Bohr model of a sodium atom showing the nucleus (11 protons, 12 neutrons) and electron shells (2,8,1).

Particle arrangement in solids, liquids and gases.

Slides

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Practice questions

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1.What is the Dalton model of the atom?
Easy
- AAtoms are indivisible and cannot be broken down into anything smaller.
- BAtoms are made of protons, neutrons and electrons.
- CAtoms have a nucleus with electrons orbiting.
- DAtoms are mostly empty space.
2.Where is the nucleus of an atom located?
Easy
- AIn the centre of the atom.
- BOrbiting the atom.
- COutside the electron shells.
- DScattered throughout the atom.
3.Which two sub-atomic particles are found in the nucleus?
Easy
- AProtons and neutrons.
- BProtons and electrons.
- CNeutrons and electrons.
- DProtons, neutrons and electrons.
4.Which sub-atomic particle orbits around the nucleus?
Easy
- AElectron
- BProton
- CNeutron
- DPositron
5.What is the charge on a proton?
Easy
- APositive
- BNegative
- CNeutral
- DNo charge
6.What is the charge on an electron?
Easy
- ANegative
- BPositive
- CNeutral
- DNo charge
7.What is the charge on a neutron?
Easy
- ANeutral
- BPositive
- CNegative
- DNo charge
8.Which sub-atomic particle has the least mass?
Easy
- AElectron
- BProton
- CNeutron
- DNucleus

More questions

9.What is a scientific model?
Easy
- AA simplified version of an object or phenomenon to help understand it.
- BA exact replica of an object or phenomenon.
- CA guess about how something works.
- DA complex mathematical equation.
10.What is peer review?
Easy
- AWhen other scientists examine new evidence to decide if it is valid.
- BWhen a scientist reviews their own work.
- CWhen the public reviews scientific research.
- DWhen a teacher grades a student's work.
11.How does the current model of the atom differ from the Dalton model?
Medium
- AThe current model shows atoms are made of smaller particles; Dalton thought atoms were indivisible.
- BThe current model says atoms are solid spheres; Dalton said they have a nucleus.
- CDalton's model included electrons; the current model does not.
- DThere is no difference; both models are the same.
12.The diagram shows a Bohr model of a sodium atom. Which part of the atom is the nucleus?
Easy
- AThe central dot
- BThe outer ring
- CThe space between rings
- DThe electrons
13.In the Bohr model of a sodium atom shown, what is the electron configuration?
Easy
- A2, 8, 1
- B1, 8, 2
- C2, 8
- D11
14.In the current model of the atom, which two sub-atomic particles are found in the nucleus?
Easy
- AProtons and neutrons
- BProtons and electrons
- CNeutrons and electrons
- DProtons, neutrons and electrons
15.A neutral atom has 8 protons. How many electrons does it have?
Easy
- A8
- B16
- C0
- DIt depends on the number of neutrons
16.The mass of a proton is approximately 1.67 × 10⁻²⁷ kg. The mass of an electron is approximately 9.11 × 10⁻³¹ kg. How many times heavier is a proton than an electron?
Medium
- AAbout 1836 times
- BAbout 2000 times
- CAbout 100 times
- DAbout 500 times
17.A lithium atom has 3 protons and 4 neutrons. What is the total number of sub-atomic particles in the nucleus?
Medium
- A7
- B3
- C4
- D10
18.Which sub-atomic particle has a negative charge?
Easy
- AElectron
- BProton
- CNeutron
- DNucleus
19.What is the charge of a neutron?
Easy
- ANo charge
- BPositive
- CNegative
- DBoth positive and negative
20.The Bohr model of a sodium atom is shown. What is the electron configuration of sodium?
Easy
- A2,8,1
- B2,8
- C2,8,8
- D2,8,2
21.In the Bohr model of a sodium atom, which part of the atom is the nucleus?
Easy
- AThe central dot
- BThe outer ring
- CThe electrons
- DThe space between shells
22.An atom has 20 neutrons and a mass number of 40. How many protons does it have?
Medium
- A20
- B40
- C60
- D10
23.Which statement about the Dalton model of the atom is correct?
Easy
- AIt states that atoms are indivisible spheres.
- BIt states that atoms contain protons and neutrons.
- CIt states that atoms have a nucleus.
- DIt states that electrons orbit the nucleus.
24.Why is peer review important in science?
Easy
- AIt helps ensure that new evidence is valid before it is published.
- BIt allows scientists to keep their research secret.
- CIt speeds up the publication process.
- DIt guarantees that all research is correct.
25.In an experiment to determine the number of protons in an atom, a scientist measures the charge on the nucleus. If the nucleus has a charge of +3.2 × 10⁻¹⁹ C, and the charge on a proton is +1.6 × 10⁻¹⁹ C, how many protons are in the nucleus?
Medium
- A2
- B3
- C4
- D5
26.A student sets up an experiment to measure the deflection of α particles by a thin gold foil. Most α particles pass straight through, but a few are deflected at large angles. What does this experimental evidence suggest about the atom?
Medium
- AThe atom is mostly empty space with a small, dense nucleus.
- BThe atom is a solid sphere of positive charge.
- CThe atom is indivisible.
- DElectrons orbit the nucleus in fixed paths.
27.In a mass spectrometer, the mass of an atom is found to be 3.82 × 10⁻²⁶ kg. The mass of a proton is 1.67 × 10⁻²⁷ kg and the mass of a neutron is 1.67 × 10⁻²⁷ kg. The atom is neutral and has 13 electrons. How many neutrons does the atom have?
Hard
- A10
- B13
- C14
- D23
28.Which sub-atomic particle is responsible for the chemical properties of an element?
Easy
- AProton
- BNeutron
- CElectron
- DNucleus
29.In an experiment, a beam of electrons is fired at a thin metal foil. The pattern of electrons that emerge is used to infer the structure of the atom. What does this experiment help determine?
Medium
- AThe size of the nucleus
- BThe charge of the electron
- CThe arrangement of electrons in the atom
- DThe mass of the proton
30.A scientist proposes a new model of the atom. Before it is accepted, other scientists review the evidence and attempt to reproduce the results. This process is called:
Easy
- AHypothesis testing
- BPeer review
- CExperimental design
- DData analysis
31.The diagram shows a Bohr model of a sodium atom. Which labelled part represents the electron shell with the highest energy?
Easy
- APart A (innermost shell)
- BPart B (second shell)
- CPart C (outermost shell)
- DPart D (nucleus)
32.The diagram shows a Bohr model of a sodium atom. What is the total number of electrons in the atom?
Easy
- A11
- B12
- C23
- D24
33.In the particle model, which state of matter has particles that are closely packed but can slide past each other?
Easy
- ASolid
- BLiquid
- CGas
- DPlasma
34.A student draws a particle diagram for a gas. Which of the following best describes the particle arrangement?
Easy
- AParticles are in fixed positions and vibrate.
- BParticles are close together but can move past each other.
- CParticles are far apart and move randomly.
- DParticles are arranged in a regular lattice.
35.What is the charge of the nucleus of an atom?
Easy
- APositive
- BNegative
- CNeutral
- DIt depends on the element
36.An atom has 6 protons and 8 neutrons. What is the mass number of this atom?
Easy
- A6
- B8
- C14
- D20
37.In the current model of the atom, which sub-atomic particle has no charge?
Easy
- ANeutron
- BProton
- CElectron
- DNucleus
38.The diagram shows a Bohr model of a sodium atom. Which labelled part represents the nucleus?
Easy
- AA
- BB
- CC
- DD
39.A student uses a model of the atom to predict the chemical behaviour of an element. Which feature of the model is most important for this prediction?
Medium
- AThe number of protons in the nucleus
- BThe number of neutrons in the nucleus
- CThe arrangement of electrons in shells
- DThe total mass of the atom
40.An atom has 11 protons and 12 neutrons. What is the total charge on its nucleus?
Medium
- A+11
- B+12
- C+23
- D0
41.The Dalton model of the atom states that atoms are indivisible.
Easy
True or false?
42.In the current model of the atom, the nucleus contains protons and electrons.
Easy
True or false?
43.A neutron has no electric charge.
Easy
True or false?
44.Scientific models are always exact representations of reality.
Easy
True or false?
45.Peer review helps ensure that new scientific evidence is valid before it is published.
Easy
True or false?
46.Which statement best describes the Dalton model of the atom?
Easy
- AAtoms are made of protons, neutrons and electrons.
- BAtoms are indivisible spheres that cannot be broken down.
- CAtoms have a nucleus with electrons orbiting around it.
- DAtoms are mostly empty space with a small nucleus.
47.Which subatomic particle has a positive charge?
Easy
- AElectron
- BNeutron
- CProton
- DNucleus
48.The diagram shows a Bohr model of an atom. Which part is the nucleus?
Easy
- AThe central dot
- BThe outer circle
- CThe space between circles
- DThe electrons
49.Arrange the following in order of increasing mass: electron, proton, neutron.
Easy
- electron
- proton
- neutron
50.Match each sub-atomic particle to its correct charge.
Easy
- Proton
- Neutron
- Electron
- Positive
- Negative
- No charge
51.Complete the sentence:
Easy
Most of the mass of an atom is contained in the ____.

Revision notes

## The Atom - Revision Notes ### Scientific Models - A **scientific model** is a simplified version of an object or phenomenon, making it easier to understand while representing key features. - Models are changed and updated over time as new evidence emerges. ### Dalton Model (Old Model) - Atoms were thought to be **indivisible** (could not be broken down into anything smaller). ### Current Model of the Atom - Atoms are made of **sub-atomic particles** (smaller than the atom itself). - Three sub-atomic particles: 1. **Protons** – positive charge, located in the **nucleus** (centre of atom). 2. **Neutrons** – neutral (no charge), also in the nucleus. 3. **Electrons** – negative charge, **orbit** around the nucleus. - Most of the mass is in the nucleus; protons and neutrons have ~2000 times more mass than an electron. - Overall atom is **neutral** because number of electrons = number of protons. ### Peer Review - **Peer review** is when other scientists examine new evidence to decide if it is valid. - Prevents incorrect models/theories from spreading. - After peer review, research can be published; other scientists may try to **reproduce** the results to check if they are repeatable. ### Key Differences: Dalton vs Current Model - Dalton: atoms are indivisible. - Current: atoms are made of protons, neutrons, and electrons.

Scientific model: A simplified version of an object or phenomenon, used to explain and predict behaviour while representing key features.
Dalton model: An early atomic model stating that atoms are indivisible and cannot be broken down into smaller parts.
Sub-atomic particle: A particle smaller than an atom; includes protons, neutrons, and electrons.
Proton: A positively charged sub-atomic particle found in the nucleus of an atom.
Neutron: A neutral (no charge) sub-atomic particle found in the nucleus of an atom.
Electron: A negatively charged sub-atomic particle that orbits the nucleus of an atom.
Nucleus: The centre of an atom, containing protons and neutrons, and most of the atom's mass.
Peer review: A process where other scientists examine new evidence to decide if it is valid before publication.

Flashcards

What is a scientific model?

A simplified version of an object or phenomenon that makes it easier to understand while still representing key features.

What is the particle model used for?

To explain and predict the behaviour of solids, liquids and gases.

What was the Dalton model of the atom?

The Dalton model stated that atoms were indivisible (could not be broken down into anything smaller).

Why are subatomic particles called subatomic?

Because they are smaller than the atom itself.

Name the three subatomic particles in the current model of the atom.

Protons, neutrons, and electrons.

What is the charge of a proton?

Positive.

Where are protons located in an atom?

In the nucleus (centre of the atom).

What is the charge of a neutron?

Neutral (no charge).

Where are neutrons located?

In the nucleus.

What is the charge of an electron?

Negative.

Where do electrons orbit?

Around the nucleus.

Which part of the atom contains most of its mass?

The nucleus (protons and neutrons have about 2000 times more mass than an electron).

Why is an atom overall neutral?

Because it has equal numbers of electrons and protons.

Which subatomic particle has the least mass?

Electron.

What is peer review?

When other scientists examine new evidence to decide whether it is valid.

Why is peer review important?

To prevent incorrect models and theories from being spread.

What happens after peer review?

New research can be published, and other scientists may try to reproduce the results to check repeatability.

How do scientific models change over time?

They are updated based on new evidence and research.

What is the nucleus of an atom?

The centre of the atom, containing protons and neutrons.

What is the difference between the Dalton model and the current model of the atom?

Dalton thought atoms were indivisible; the current model shows atoms are made of subatomic particles (protons, neutrons, electrons).

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