Reading the Periodic Table



Reading the Periodic Table

Look at the periodic table of the elements and answer the following questions:

Background

1. Each element is identified by an abbreviation (H = hydrogen, Li = lithium, Na = sodium, K = potassium and so on - see the page following the table for a complete list). Find these elements in the table and identify the group to which each belongs. Groups are designated by a Roman numeral at the top of each column.

Table 2. Group Identification

|Atom |  Group   |

|hydrogen   |  |

|lithium   |  |

|sodium   |  |

|potassium   |  |

2. Elements in each group have common structural and functional properties. For example, the elements in Group IA each have one electron in the outer shell of their atoms and are thus highly reactive. They tend to lose this electron in chemical reactions and to become ions with a single positive charge (e.g., H+, Na+, K+). Atoms in Group IIA each have two electrons in their outer orbit which are also easily given up to form ions. What is the charge on these ions? _____________ How would you write the abbreviations for calcium and magnesium ions?

3. In the periodic table that follows, the number of protons (and in most cases, also of electrons and neutrons) is designated by the number in the lower left corner of each box in the periodic table (e.g., H has 1, Li has 3, and Na has 11 protons). This is the atomic number of the element. What is the atomic number of:

|phosphorus (P)? |_____________ |

|sulfur (S)? |_____________ |

4. As noted previously, each neutron and proton has a mass of one, while the weight of each electron is infinitesimal (close to zero). Thus, helium (He ) has an atomic number of 2, meaning it generally contains 2 protons, 2 electrons, and 2 neutrons. Helium has an atomic weight of 4.003, as shown at the top of the box. What is the atomic weight of:

|carbon (C) |_____________ |

|nitrogen |_____________ |

|oxygen |_____________ |

5. Elements are arranged in the periodic table from left to right and top to bottom in order of increasing mass. The table starts with hydrogen (with an atomic number of one) and goes to unnilennium (with an atomic number of 109). There is an element for each atomic number in between, except for 108 which has not yet been observed. What element has an atomic number of 26? ________________ Is this element important in living things? ____ Explain.

6. Only the lighter elements occur in living things. In particular, living organisms are composed of about 25 of the elements in the top four rows of the periodic table. For example, what element has an atomic weight of 40.08 and where does this occur in living things?

7. Approximately 25 elements occur in living things. Six of these 25 elements are of critical importance in that they comprise the four major groups of molecules found in living organisms: carbohydrates, lipids, proteins and nucleic acids. These elements are called CHNOPS for short.

To Do

Find the six elements in the periodic table and complete the chart below. Learn all you can about these six atoms.

Table 3. Some Characteristics of CHNOPS

|Abreviation |Atom |Atomic Number |Atomic Weight |Group |

|C |carbon |  |  |  |

|H |hydrogen |  |  |  |

|N |nitrogen |  |  |  |

|O |oxygen |  |  |  |

|P |phosphorous |  |  |  |

|S |sulfur |  |  |  |

Questions

8. Which of the other five elements in CHNOPS is most like oxygen?

9. Which of the other five elements in CHNOPS is most like nitrogen?

10. Which element in CHNOPS has the greatest mass?

11. Which element in CHNOPS has the least mass?

Describe

12. Describe how your body obtains oxygen.

13. What is the primary means by which your body obtains phosphorus, carbohydrates and fats?

14. How does your body obtain the hydrogen it needs?

15. Can your body obtain what it needs by eating carbohydrates or fats alone? Which of the CHNOPS elements are completely absent from carbohydrates and fats?

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