General Chemistry Chapter 2 Part 1 Answer Key

1. The element symbol for copper is Cu. 2. An atom of the isotope ¹³³Cs contains how many protons (p), neutrons (n), and electrons (e)? A) 55 p, 55 n, 55 e 133 = 55 + x B) 55 p, 78 n, 55 e C) 133 p, 133 n, 133 e 78 = x D) 55 p, 133 n, 55 e E) 133 p, 55 n, 55 e 133 = 55 + x 3. The symbol Sr represents the element symbol of strontium. 4. What does the nucleus of an atom contain? Protons and neutrons 5. Which two particles of the atom have nearly identical masses? Protons and neutrons **A protons has a mass of 1. 673 × 10 and a neutron has a mass of 1. 675 × 10 −27 −27 𝑘𝑔, an electron has a mass of 9. 109 × 10 −31 𝑘𝑔, 𝑘𝑔. 6. What element with a mass number of 100 has 56 neutrons in its nucleus? Ruthenium (Ru). 7. What is the mass number for an atom of Xenon containing 54 protons and 75 neutrons? 129 **Calculate the mass number using the given number of protons and neutrons. For example, if there are 54 protons and 75 neutrons, the mass number can be calculated like this: 54+75 = 129 8. The atomic mass of germanium (Ge) on the periodic table is 72.630 amu. Which of the following best explains why the atomic mass is a fraction between 72 and 73? The presence of different isotopes 9. An unknown element X has the following isotopes: ² X (80.50% abundant, mass = 25.03 amu) and ² X (19.50% abundant, mass = 26.98 amu). What is the average atomic mass of X in amu? 25.4 AMU **Average atomic mass = ( 0.8050 × 25.03 ) + ( 0.1950 × 26.98 ) = ( 20.15 ) + ( 5.261 ) = 25.41 amu 10. The empirical formula of a covalent compound is CH . Which of the following is NOT a possible chemical formula for this compound? C₆H₁₀ ** An empirical formula shows the ratio of each element to one another in the formula. C H has a ratio of 3 carbon atoms to every 5 hydrogen atoms. The empirical formula for C H is 𝐶 3𝐻5