Basic Chemistry: Atomic Structure and Laws of Matter

Who were the first to propose that matter is composed of small, indestructible particles?

Leucippus and his student Democritus.

What did Democritus state about atoms?

He proposed that atoms existed in different shapes and sizes and moved randomly through empty space.

Which philosophers did not accept the atomic theory proposed by Leucippus and Democritus?

Plato and Aristotle.

What was John Dalton's contribution to atomic theory?

He provided convincing evidence supporting the atomic ideas of Leucippus and Democritus and formulated Dalton's atomic theory.

What are the key points of Dalton's atomic theory?

1. Each element is composed of tiny, indestructible particles called atoms. 2. All atoms of a given element have the same mass and properties. 3. Atoms combine in simple, whole-number ratios to form compounds. 4. Atoms of one element cannot change into atoms of another element.

What does the Law of Conservation of Mass state?

Mass is neither created nor destroyed; it can inter-transform between different forms, but the total mass remains the same during chemical or physical changes.

Provide an example of a physical change.

Ice melting to water.

What happens to the matter that composed a log when it burns in a campfire?

The matter reacts to form gases released into the air.

What is the Law of Definite Proportions?

All samples of a given compound have the same proportions of their constituent elements, regardless of their source or preparation.

Who formulated the Law of Definite Proportions?

Joseph Proust in 1797.

What is another name for the Law of Definite Proportions?

The law of constant composition.

What is the significance of Dalton's atomic theory in chemistry?

It laid the foundation for modern chemistry by explaining the behavior of matter and the laws governing chemical reactions.

What is an example of a chemical change?

A reaction occurring that forms a new compound.

What did Dalton suggest about the properties of atoms in different elements?

Atoms of different elements have different masses and properties.

How did Dalton's atomic theory explain the law of multiple proportions?

It stated that when elements combine, they do so in simple whole-number ratios, leading to different compounds.

What is the relationship between mass and chemical reactions according to the Law of Conservation of Mass?

The total mass before and after a chemical reaction remains constant.

What did the early atomic ideas propose about the nature of matter?

Matter is made up of small, indestructible particles called atoms.

What was Plato and Aristotle's view on the composition of matter?

They believed matter had no smallest parts and was composed of varying proportions of fire, air, earth, and water.

What is a misconception about the mass of a log after it burns?

That the mass of the ash is the same as the mass of the log; in reality, gases are released, reducing the mass.

What did Dalton's atomic theory state about chemical reactions?

In a chemical reaction, atoms change only the way they are bound together with other atoms.

How did Dalton's theory differ from earlier beliefs about matter?

It introduced the concept of atoms as indivisible particles, contrasting with the belief in continuous matter.

What evidence did Dalton provide to support his atomic theory?

Observations on chemical reactions and the behavior of gases.

What is the mass ratio of oxygen to hydrogen in the decomposition of water?

The mass ratio is 8:1, as 16.0 grams of oxygen and 2.0 grams of hydrogen are produced from 18.0 grams of water.

If a sample of ammonia contains 10.0 grams of hydrogen, how many grams of nitrogen does it contain?

The answer is 14 grams.

How do you demonstrate that two samples of a compound are consistent with the Law of Definite Proportions?

By calculating the mass ratio of one element to another for both samples and showing they are the same.

What are the masses of oxygen and carbon produced from the first sample of carbon dioxide decomposition?

25.6 grams of oxygen and 9.60 grams of carbon.

What are the masses of oxygen and carbon produced from the second sample of carbon dioxide decomposition?

21.6 grams of oxygen and 8.10 grams of carbon.

What is the Law of Multiple Proportions?

It states that when two elements form two different compounds, the masses of one element that combine with a fixed mass of the other can be expressed as a ratio of small whole numbers.

What is the mass ratio of oxygen to carbon in carbon dioxide?

2.67 grams of oxygen reacts with 1 gram of carbon.

What is the mass ratio of oxygen to carbon in carbon monoxide?

1.33 grams of oxygen to every 1 gram of carbon.

How do you demonstrate that two compounds are consistent with the Law of Multiple Proportions?

By calculating the ratio of the mass of oxygen from one compound to the mass of oxygen in the other and showing it is a small whole number.

What are the mass ratios of oxygen in nitrogen dioxide and dinitrogen monoxide?

Nitrogen dioxide contains 2.28 grams of oxygen to every 1.00 gram of nitrogen, while dinitrogen monoxide contains 0.570 grams of oxygen to every 1.00 gram of nitrogen.

What is the significance of the ratios in the Law of Multiple Proportions?

The ratios of the masses of the elements in different compounds are small whole numbers, indicating a consistent relationship.

What is the first step in solving a problem using the Law of Definite Proportions?

Calculate the mass ratio of one element to another in the samples.

Why is it important to divide the larger mass by the smaller mass when calculating ratios?

To ensure the ratio is simplified and expressed in a consistent manner.

What is an example of two compounds that illustrate the Law of Multiple Proportions?

Carbon monoxide and carbon dioxide.

What is the purpose of the examples provided in the notes?

To illustrate how the laws of definite and multiple proportions apply to chemical compounds.

What is the mass of oxygen produced from the first sample of carbon monoxide decomposition?

17.2 grams of oxygen.

What is the mass of carbon produced from the second sample of carbon monoxide decomposition?

7.88 grams of carbon.

How can the results of two samples of a compound be shown to be consistent with the Law of Definite Proportions?

By ensuring the mass ratios calculated for both samples are equal.

What is the significance of John Dalton's contribution to chemistry?

He published the Law of Multiple Proportions, which advanced the understanding of chemical combinations.

What is the mass ratio of oxygen in nitrogen dioxide compared to dinitrogen monoxide?

The ratio of 2.28 grams of oxygen in nitrogen dioxide to 0.570 grams in dinitrogen monoxide is a small whole number.

What is the total mass of the water sample used in the Law of Definite Proportions example?

18.0 grams.

What does the consistent mass ratio of elements in compounds indicate?

It confirms the validity of the laws of definite and multiple proportions in chemical reactions.

How do hydrogen and oxygen demonstrate the law of multiple proportions?

Water has a ratio of 0.125 grams of hydrogen to 1.00 gram of oxygen, while hydrogen peroxide has a ratio of 0.0625 grams of hydrogen to 1.00 gram of oxygen, showing consistent small whole number ratios.

What is the difference between the law of definite proportions and the law of multiple proportions?

The law of definite proportions applies to two or more samples of the same compound, while the law of multiple proportions applies to two different compounds containing the same two elements.

What did J.J. Thomson discover through his cathode ray experiments?

He discovered the electron, a negatively charged particle present in all atoms.

What are the properties of cathode rays as observed by J.J. Thomson?

Cathode rays travel in straight lines, are independent of the material of the cathode, and carry a negative electrical charge.

How did J.J. Thomson measure the charge-to-mass ratio of cathode ray particles?

He deflected the particles using electric and magnetic fields.

What did Robert Millikan's oil drop experiment determine?

It determined the charge of a single electron by measuring the electric field strength required to halt the free fall of oil drops.

What is the significance of the charge measured in Millikan's oil drop experiment?

The charge on any oil drop was always a whole-number multiple of the fundamental charge of a single electron.

What is the fundamental charge of a single electron?

The fundamental charge is the smallest unit of electric charge, which is a whole-number multiple observed in Millikan's experiment.

What did the results of the hydrogen and oxygen experiments illustrate about chemical compounds?

They illustrate that different compounds can form from the same elements in different ratios, consistent with the law of multiple proportions.

What is the role of the cathode in J.J. Thomson's experiments?

The cathode is the negatively charged electrode from which cathode rays originate.

What is the role of the anode in J.J. Thomson's experiments?

The anode is the positively charged electrode that attracts the negatively charged cathode rays.

What did Thomson's experiments reveal about the composition of cathode rays?

They revealed that cathode rays are composed of negatively charged particles, now known as electrons.

What was the outcome of J.J. Thomson's work on the understanding of atomic structure?

His work led to the identification of the electron as a fundamental component of atoms.

How did the law of multiple proportions relate to the ratios found in the hydrogen and oxygen compounds?

The ratios of hydrogen in water and hydrogen peroxide demonstrate that different compounds can be formed from the same elements in simple whole number ratios.

What is the significance of the charge-to-mass ratio in Thomson's findings?

It provided insight into the properties of electrons and their behavior in electric and magnetic fields.

Why is the discovery of the electron important in chemistry?

It fundamentally changed the understanding of atomic structure and the nature of chemical bonding.

What does the law of definite proportions state?

It states that a chemical compound always contains its component elements in fixed ratio by mass.

What was the method used by Millikan to determine the mass of oil drops?

He determined the mass from the radii (size) and density of the oil drops.

What is the relationship between the law of definite proportions and chemical compounds?

It ensures that compounds are formed from elements in specific, consistent ratios regardless of the sample size.

How did Thomson's findings contribute to modern atomic theory?

They provided evidence that atoms are not indivisible and contain smaller particles, leading to the development of the modern atomic model.

What was the main purpose of Millikan's Oil Drop Experiment?

To determine the charge-to-mass ratio for an electron.

What model did J.J. Thomson propose for the structure of the atom?

The plum-pudding model, which suggested that negatively charged electrons were embedded in a positively charged sphere.

What was the significant finding of Rutherford's Gold Foil Experiment?

Most particles passed through the foil, but some were deflected or bounced back, indicating that atoms contain large regions of empty space and dense matter.

What are the three basic parts of the nuclear theory of the atom?

1. Most of the atom's mass and all positive charge are in the nucleus. 2. Most of the atom's volume is empty space. 3. The number of electrons equals the number of protons, making the atom electrically neutral.

What discovery did Rutherford and James Chadwick make regarding neutrons?

They discovered that neutrons are neutral particles in the nucleus that account for the missing mass not explained by protons.

What is the charge and mass comparison between protons, neutrons, and electrons?

Protons and neutrons have nearly identical masses, while electrons have much less mass. Protons are positively charged, electrons are negatively charged, and neutrons have no charge.

How does the charge of protons compare to the charge of electrons?

The charge of protons and electrons is equal in magnitude but opposite in sign.

What is the mass of an electron compared to protons and neutrons?

The mass of an electron is significantly smaller than that of both protons and neutrons.

What conclusion did Rutherford draw from the deflection of particles in his Gold Foil Experiment?

He concluded that matter is not uniform and contains large regions of empty space with dense regions of matter.

What did Millikan's experiment contribute to the understanding of electrons?

It provided a method to calculate the charge of an electron, leading to the determination of its mass.

What is the significance of the plum-pudding model in atomic theory?

It was the first widely accepted model that described the atom as a mixture of positive and negative charges.

What role do neutrons play in the atomic nucleus?

Neutrons contribute to the mass of the nucleus and help stabilize it, as they have no charge.

What is the relationship between the number of protons and electrons in a neutral atom?

In a neutral atom, the number of protons equals the number of electrons.

What did Rutherford's model replace in atomic theory?

It replaced the plum-pudding model with a new understanding of the atom's structure, emphasizing the nucleus.

What is the primary characteristic of the nucleus in the nuclear atom model?

It contains most of the atom's mass and all of its positive charge.

How did Rutherford's findings challenge previous atomic models?

They showed that atoms have a dense nucleus rather than being a uniform distribution of charge.

What is the significance of the term 'subatomic particles'?

Subatomic particles are the building blocks of atoms, including protons, neutrons, and electrons.

What experimental evidence did Millikan provide regarding electrons?

He provided evidence for the quantization of electric charge by measuring the charge of oil drops.

What is the charge of a neutron?

A neutron has no electrical charge.

How did the discovery of neutrons impact the understanding of atomic mass?

It explained the discrepancy in atomic mass that could not be accounted for by protons alone.

What is the main takeaway from the Gold Foil Experiment regarding atomic structure?

Atoms consist mostly of empty space with a dense nucleus at the center.