Science Chapter 3: Atoms Review

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Questions and Answers

Why is Democritus's view of matter considered only an idea, while Dalton's view is considered a theory?

Democritus's idea of matter does not relate atoms to a measurable property, while Dalton's theory can be tested through quantitative experimentation.

Give an example of a chemical or physical process that illustrates the law of conservation of mass.

A glass of ice cubes will have the same mass when the ice has completely melted into liquid water, even though its volume will change.

State two principles from Dalton's atomic theory that have been revised as new information has become available.

Atoms are divisible into smaller particles called subatomic particles. A given element can have atoms with different masses, called isotopes.

What parts of Dalton's atomic theory are illustrated by the reaction 2H2 O2 → 2H2O?

Atoms cannot be subdivided, created, or destroyed. Atoms of different elements combine in simple, whole-number ratios to form compounds. Signup and view all the answers

If 3 g of element C combine with 8 g of element D to form compound CD, how many grams of D are needed to form compound CD2?

16 g Signup and view all the answers

Which law do these data illustrate?

the law of definite proportions Signup and view all the answers

State the law regarding chemical compounds.

A chemical compound contains the same elements in exactly the same proportions by mass regardless of the sample or the source of the compound. Signup and view all the answers

Calculate the ratio of the masses of nitrogen that combine with oxygen for compound NO.

2.0 Signup and view all the answers

Calculate the ratio of the masses of nitrogen that combine with oxygen for compound NO2.

2.0 Signup and view all the answers

Calculate the ratio of the masses of nitrogen that combine with oxygen for compound NO4.

4.0 Signup and view all the answers

Which law do these data illustrate in relation to nitrogen and oxygen compounds?

the law of multiple proportions Signup and view all the answers

In cathode-ray tubes, the cathode ray is emitted from the negative electrode, which is called the?

cathode Signup and view all the answers

The smallest unit of an element that can exist either alone or in molecules is called what?

atom Signup and view all the answers

A positively charged particle found in the nucleus is called a(n)?

proton Signup and view all the answers

A nuclear particle that has no electrical charge is called a(n)?

neutron Signup and view all the answers

The subatomic particles that are least massive and most massive, respectively, are the?

electron and neutron Signup and view all the answers

What property of the cathode ray is shown by various phenomena including its deflection by a magnetic field?

The particles that compose cathode rays are negatively charged. Signup and view all the answers

How would the electrons produced in a cathode-ray tube filled with neon gas compare with those from chlorine gas?

The electrons produced from neon gas and chlorine gas would behave in the same way because electrons do not differ from element to element. Signup and view all the answers

Is an atom positively charged, negatively charged, or neutral?

Atoms are neutral. Signup and view all the answers

Explain how an atom can exist in a neutral state.

Atoms consist of a positively charged nucleus, made up of protons and neutrons, that is surrounded by a negatively charged electron cloud. Signup and view all the answers

Before Rutherford's experiment, which illustration of the atom was believed to be correct?

before Rutherford's experiment Signup and view all the answers

After Rutherford's experiment, which illustration of the atom was believed to be correct?

After Rutherford's experiment Signup and view all the answers

What is the proton known for?

The proton, a positive and relatively massive particle, should be located in the nucleus. Signup and view all the answers

What is the neutron known for?

The neutron, a neutral and relatively massive particle, should be located in the nucleus. Signup and view all the answers

Where is the electron located?

The electron, a negative particle with a low mass, should be located in the cloud surrounding the nucleus. Signup and view all the answers

Study Notes

Democritus vs. Dalton

Democritus considered matter as indivisible atoms, but his ideas lacked measurable properties.
Dalton's atomic theory involves quantifiable experimentation, leading to its acceptance as a scientific theory.

Law of Conservation of Mass

Melting ice cubes exemplify this law, as the mass remains unchanged despite a change in state from solid to liquid (ice to water).

Revisions in Dalton's Theory

Atoms can be subdivided into subatomic particles like protons, neutrons, and electrons.
Elements may have isotopes, which are atoms with the same number of protons but different masses.

Water Formation Reaction

The reaction 2H₂ + O₂ → 2H₂O demonstrates mass conservation, affirming that mass of products equals mass of reactants.
Illustrates that atoms combine in simple, whole-number ratios and cannot be created or destroyed.

Compound Formation Example

Combining 3 g of element C with 8 g of D yields compound CD, requiring 16 g of D to form CD₂.

Law of Definite Proportions

Each chemical compound consists of its elements in fixed mass proportions, regardless of sample source.

Ratios of Nitrogen to Oxygen Compounds

In compounds such as NO, NO₂, and NO₄, specific mass ratios of nitrogen to 1 g of oxygen illustrate multiple proportions.

Cathode Rays

Cathode rays are emitted from the cathode (negative electrode) in cathode-ray tubes and consist of negatively charged particles.

Fundamental Particles

An atom is the smallest unit of an element that retains its properties, consisting of protons, neutrons, and electrons.
Protons are positively charged particles found in the nucleus.
Neutrons are neutral particles located in the nucleus alongside protons.
Electrons are negatively charged and exist in a cloud surrounding the nucleus.

Atomic Charge

Atoms overall are neutral due to the balance of positive protons and negative electrons.
The nucleus carries a positive charge, while electrons contribute a negative charge, resulting in electrical neutrality.

Historical Models of the Atom

Pre-Rutherford, atoms were depicted with electrons embedded in a positive "soup" (Thomson's model).
After Rutherford's gold foil experiment, the nuclear model was accepted, showing a dense nucleus and surrounding electron cloud.

Electron Location

Electrons are located in the region outside the nucleus, forming a cloud structure around it, due to their low mass and negative charge.

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Description

Test your understanding of atoms and their role as the building blocks of matter with this flashcard review of Chapter 3. Explore key concepts like Democritus's idea versus Dalton's theory and the law of conservation of mass. Perfect for reinforcing your knowledge in chemistry.