History of the Universe
October 5, 2015
6. Briefly describe the structure and size of an atom. How big is the nucleus in comparison to the entire atom?
Atoms are extremely small; millions of atoms could fit end to end across a period at the end of a sentence. Protons and neutrons are found in the tiny nucleus at the center of the atom. The rest of the atom’s volume is made up of electrons, which surround the nucleus. The nucleus is very small compared to the atom as a whole, but it contains a majority of the atom’s mass.
7. What determines an atom’s atomic number? What determines its atomic mass number? Under what conditions are two atoms different ...view middle of the document...
Describe the conditions that would cause us to see each of the three basic types of spectra. What do we see in the Sun’s spectrum shown on the opening page of this chapter?
An incandescent light bulb is a rainbow of color that spans a broad range of wavelengths without interruption is a continuous spectrum. A low-density cloud of gas emits light only at specific wavelengths that depend on its composition and temperature; this spectrum consists of bright emission lines against a black background so it is called an emission line spectrum. If a cloud of gas lies between us and a light bulb, the cloud absorbs light of specific wavelengths and shows dark absorption lines over a background rainbow—we call this the absorption line spectrum. We see an absorption line spectrum in the picture on the opening page because there are dark sections showing where the wavelengths were absorbed.
13. How can we use emission or absorption lines to determine the chemical composition of a distant object?
Hydrogen emits and absorbs light at specific wavelengths; therefore, if you look at a distant could that produces a certain spectrum with certain absorption lines, you know it is made of hydrogen. Every chemical and its ions leave different chemical fingerprints.
40. a) The most common form of iron has 26 protons and 30 neutrons. State its atomic number, atomic mass number, and number of electrons (if it is neutral).
The atomic number is 26, atomic mass is 56, and there are 26 electrons.
b) Consider the following three atoms: Atom 1 has 7 protons and 8 neutrons; atom 2 has 8 protons and 7 neutrons; atom 3 has 8 protons and 8 neutrons. Which two are isotopes of the same element?
Atom 2 and atom 3 are isotopes of the same element.
c) Oxygen has atomic number 8. How many times must an oxygen atom be ionized to create an O+5 ion? How many electrons are in an O+5 ion?
An oxygen atom would need to be ionized 5 times. There are 3 electrons in an O+5 ion.
41. a) What are the atomic number and atomic mass number of a fluorine atom with 9 protons and 10 neutrons? If we could add a proton to this fluorine...