91影视

Section 2.3 describes the postulates of Dalton鈥檚 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鈥檚 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?

The contributions of J. J. Thomson and Ernest Rutherford led the way to today鈥檚 understanding of the structure of the atom. What were their contributions?

What is the modern view of the structure of the atom?

The number of protons in an atom determines the identity of the atom. What does the number and arrangement of the electrons in an atom determine? What does the number of neutrons in an atom determine?

If the volume of a proton were similar to the volume of an electron, how will the densities of these two particles compare to each other?

For lighter, stable isotopes, the ratio of the mass number to the atomic number is close to a certain value. What is the value? What happens to the value of the mass number to atomic number ratio as stable isotopes become heavier?

List some characteristic properties that distinguish the metallic elements from the nonmetallic elements

Consider the elements of Group 4A (the 鈥渃arbon family鈥�): C, Si, Ge, Sn, and Pb. What is the trend in metallic character as one goes down this group? What is the trend in metallic character going from left to right across a period in the periodic table?

Chlorine has two natural isotopes: \(_{17}^{37} \mathrm{Cl}\) and 35 17 \(\mathrm{Cl}\) Hydrogen reacts with chlorine to form the compound HCl. Would a given amount of hydrogen react with different masses of the two chlorine isotopes? Does this conflict with the law of definite proportion? Why or why not?

Before an electrocardiogram (ECG) is recorded for a cardiac patient, the ECG leads are usually coated with a moist paste containing sodium chloride. Why is sodium chloride applied to the leads?