## Chemistry: Principles and Practice (3rd Edition)

(a) $_{5}^{11}$B (b) $_{25}^{55}$Mn (c) $_{14}^{28}$Si
(a) If an element contains 5 protons, that means that it has an atomic number of 5 as well because the atomic number is equal to the number of protons. To write the complete symbol, we first locate the element with an atomic number of 5 on the periodic table. We see that this element is boron, and its chemical symbol is B. We write the atomic number to the left of the chemical symbol as a subscript. The mass number is the number of protons and the number of neutrons. The number of protons is the same number as the element's atomic number. The number of neutrons is already given in the problem. So we have the number of protons as 5 and the number of neutrons as 6. When we add 5 to 6, we get 11; this is the mass number. We write the mass number as a superscript to the left of the chemical symbol as well. The complete symbol for this particular atom of is $_{5}^{11}$B. (b) If an element contains 25 protons, that means that it has an atomic number of 25 as well because the atomic number is equal to the number of protons. To write the complete symbol, we first locate the element with an atomic number of 25 on the periodic table. We see that this element is manganese, and its chemical symbol is Mn. We write the atomic number to the left of the chemical symbol as a subscript. The mass number is the number of protons and the number of neutrons. The number of protons is the same number as the element's atomic number. The number of neutrons is already given in the problem. So we have the number of protons as 25 and the number of neutrons as 30. When we add 25 to 30, we get 55; this is the mass number. We write the mass number as a superscript to the left of the chemical symbol as well. The complete symbol for this particular atom of is $_{25}^{55}$Mn. (c) If an element contains 14 protons, that means that it has an atomic number of 14 as well because the atomic number is equal to the number of protons. To write the complete symbol, we first locate the element with an atomic number of 14 on the periodic table. We see that this element is silicon, and its chemical symbol is Si. We write the atomic number to the left of the chemical symbol as a subscript. The mass number is the number of protons and the number of neutrons. The number of protons is the same number as the element's atomic number. The number of neutrons is already given in the problem. So we have the number of protons as 14 and the number of neutrons as 14. When we add 14 to 14, we get 28; this is the mass number. We write the mass number as a superscript to the left of the chemical symbol as well. The complete symbol for this particular atom of is $_{14}^{28}$Si.