Section I-5 describes the postulates of Dalton's atomic...

Section I-5 describes the postulates of Dalton's atomic theory. With some modifications, these postulates hold up very well regarding how we view elements, compounds, and chemical reactions today. Answer the following questions concerning Dalton's atomic theory and the modifications made today. a. The atom can be broken down into smaller parts. What are the smaller parts? b. How are atoms of hydrogen identical to each other and how can they be different from each other? c. How are atoms of hydrogen different from atoms of helium? How can H atoms be similar to He atoms? d. How is water different from hydrogen peroxide $\left(\mathrm{H}_{2} \mathrm{O}_{2}\right)$ even though both compounds are composed of only hydrogen and oxygen? e. What happens in a chemical reaction and why is mass conserved in a chemical reaction?

Section I-5 describes the postulates of Dalton's atomic theory. With some modifications, these postulates hold up very well regarding how we view elements, compounds, and chemical reactions today. Answer the following questions concerning Dalton's atomic theory and the modifications made today.
a. The atom can be broken down into smaller parts. What are the smaller parts?
b. How are atoms of hydrogen identical to each other and how can they be different from each other?
c. How are atoms of hydrogen different from atoms of helium? How can H atoms be similar to He atoms?
d. How is water different from hydrogen peroxide $\left(\mathrm{H}_{2} \mathrm{O}_{2}\right)$ even though both compounds are composed of only hydrogen and oxygen?
e. What happens in a chemical reaction and why is mass conserved in a chemical reaction?

Key Concepts

Dalton's Atomic Theory

Dalton's atomic theory was an early attempt to explain the nature of matter by proposing that elements are composed of small, indivisible particles called atoms, which combine in fixed proportions to form compounds. While Dalton's postulates laid the groundwork for modern atomic theory, subsequent discoveries (such as subatomic particles) required modifications to his ideas, leading to our current understanding of atomic structure and behavior in chemical reactions.

Subatomic Particles

Modern atomic theory reveals that atoms are composed of even smaller particles: protons, neutrons, and electrons. Protons and neutrons reside in the nucleus, defining the element's identity and mass, while electrons orbit the nucleus and are involved in chemical reactions. This concept explains how atoms can be broken down and their internal structure plays a crucial role in the properties and behavior of elements.

Isotopes

Although atoms of a given element share the same number of protons, they can differ in the number of neutrons, resulting in different isotopes of that element. This variation can affect the atom's mass and some physical properties, while the chemical behavior remains largely the same because the number of protons (which defines the element) and the number of electrons (which influence chemistry) do not change.

Elemental Identity

Elements are defined by the number of protons in the nucleus, known as the atomic number. Atoms of different elements, such as hydrogen and helium, differ in their number of protons and neutrons, which influences their chemical properties and behavior. However, atoms of different elements can share similar behavior under certain conditions, like being gases under the same temperature and pressure, but their elemental identities remain distinct due to their unique nuclear compositions.

Molecular Structure

The specific arrangement and bonding of atoms in a molecule determine its chemical identity and properties. Even if compounds are composed of the same types of atoms, like hydrogen and oxygen, differences in the number of atoms or the way they are bonded—as seen in water (H2O) versus hydrogen peroxide (H2O2)—result in completely different substances with distinct physical and chemical characteristics.

Chemical Reactions and the Law of Conservation of Mass

In a chemical reaction, atoms are rearranged to form new compounds; bonds between atoms are broken and new ones formed, but the atoms themselves are conserved. This reorganization respects the law of conservation of mass, which states that mass is neither created nor destroyed during a chemical reaction, ensuring that the total mass of the reactants equals the total mass of the products.

Transcript

00:01 So delta's atomic theory makes certain assertions.

00:03 Of these assertions, one of them is that atoms can be broken down into smaller parts.

00:09 Now, what does that mean? well, if we actually break down an atom, we'll see that it has three major parts to it.

00:18 So first is the electron cloud on the outside, and then the second part is the protons at the center, and then the third part is a neutron at the center.

00:29 So those are the three parts of your atom.

00:31 So we have the electron cloud, which dalton actually didn't know about that totally yet.

00:38 But we know that we can break up atoms to smaller parts, and this is what makes them up.

00:42 We have our protons, and the third small part is our neutrons.

00:52 Now, you might be wondering, what makes something like a hydrogen atom different from another hydrogen atom? so let's say we have a hydrogen atom with a mass of one, atomic number of one.

01:13 And we also have a hydrogen with, let's say, an atomic mass of two, and an atomic number of one.

01:23 Well, what's similar about these two hydrogen atoms is that one, they're both hydrogen.

01:30 They're both hydrogen.

01:31 That's really nice.

01:34 Two, same atomic number.

01:39 So let's put a little number sign, same atomic number.

01:42 And then three, let's see, they're going to behave chemically similarly.

01:51 I behave similarly.

02:00 Now one difference though you've probably noticed is the one in the two.

02:04 So what is that one in the two coming from? so the mass is determined by the protons and neutrons and we know that the protons will determine the actual element so we know it's got to stay at one.

02:17 However, they have different amounts of neutrons.

02:21 I'll put that in red.

02:22 They have different amounts of neutrons.

02:29 Have different amounts of neutrons.

02:40 But how about different types of elements? so what if i have now hydrogen and helium? so i'll put hydrogen over here, so i'll put helium over there.

02:57 So what about hydrogen and helium? how are these different? well, in this case, their protons are different...

Please give Ace some feedback