# 2.E: Elements, Atoms, and the Periodic Table (Exercises)

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1. If the atomic radius of sodium atoms is 1.86 × 10−10 m, how many sodium atoms are needed to make a line that is 1.00 cm in length?

2. If the atomic radius of osmium atoms is 1.34 × 10−10 m, how many osmium atoms are needed to make a line that is 5.85 m in length?

3. What might be the electron configuration of K+, an atom that has lost an electron?

4. What might be the electron configuration of Cl, an atom that has gained an additional electron?

5. The electron configuration of the Ti atom is 1s22s22p63s23p64s23d2. What is the valence shell electron configuration of Ti?

6. The electron configuration of the Ge atom is 1s22s22p63s23p64s23d104p2. What is the valence shell electron configuration of Ge?

7. What is the mass of an electron in atomic mass units?

8. In a footnote in this chapter, an alpha particle was defined as a particle with 2 protons and 2 neutrons. What is the mass, in grams, of an alpha particle? (Hint: what element does an alpha particle resemble?)

9. A sample of the nonexistent element mythium consists of 25.59% of an isotope with mass number 580, 32.74% of an isotope with mass number 582, and 41.67% of an isotope with mass number 581. What is the atomic mass of mythium?

10. Because the distribution of isotopes is different on different planets in the solar system, the average atomic mass of any element differs from planet to planet. Assume that on Mercury, a rather hot planet, there is more deuterium left in the atmosphere than on Earth, so that 92.55% of the hydrogen on Mercury is 1H, while the remainder is 2H. What is the atomic mass of hydrogen on Mercury?

11. The compound that sodium makes with chlorine has sodium and chlorine atoms in a 1:1 ratio. Name two other elements that should make a compound having a 1:1 ratio of atoms with sodium.

12. The compound that magnesium makes with oxygen has magnesium to oxygen atoms in a 1:1 ratio. Name two other elements that should make a compound having a 1:1 ratio of atoms with magnesium.

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