Given the background: The general trend in electronegativity is that the value increases from left to right across a row in the periodic table and decreases down a column. The most electronegative element is fluorine, which has a value of 4.0. As discussed in the lesson "Trends in the Periodic Table," electronegativity increases across a row as the number of protons in the nucleus increases and therefore has a stronger pull. Electronegativity decreases down a column due to an increased effect of electron shielding in larger atoms. and the situation: Mike has to learn more about the periodic table for his chemistry exam. To make things easier for him he chose two elements from the table, element A and element B. Element A has higher electronegativity and element B has lower eletronegativity. David found it easier to learn about elements by comparing their properties. Answer the following question: Which element would have less protons in the nucleus, element A or element B?
Ans: element B

Given the background: The Human Immunodeficiency Virus ( HIV ) is the virus that causes Acquired Immunodeficiency Syndrome ( AIDS ). Most researchers believe that the HIV originated in sub-Saharan Africa during the 20th century. HIV is transmitted by sexual contact and by contact with infected bodily fluids, such as blood, semen, breast milk, and vaginal secretions. It is also passed from mother to fetus. HIV is now a pandemic , with an estimated (as of 2008) 38.6 million people now living with the disease worldwide. It is estimated that AIDS has killed more than 25 million people since it was first recognized in 1981. For further information about HIV/AIDS, see the CDC (Centers for Disease Control and Prevention) web site at http://www.cdc.gov/hiv/resources/factsheets/ . and the situation: Dean and Paul both went to volunteered in Africa. They had a blood test when they came back. Paul had been infected with the HIV virus while Dean was healthy and clean. Answer the following question: Which friend has a virus that is transmitted by sexual contact?
Ans: Paul

Given the background: Cancer is a disease that causes cells to divide out of control. Normally, the body has systems that prevent cells from dividing out of control. But in the case of cancer, these systems fail. Cancer is usually caused by mutations. Mutations are random errors in genes. Mutations that lead to cancer usually happen to genes that control the cell cycle. Because of the mutations, abnormal cells divide uncontrollably. This often leads to the development of a tumor. A tumor is a mass of abnormal tissue. As a tumor grows, it may harm normal tissues around it. Anything that can cause cancer is called a carcinogen . Carcinogens may be pathogens, chemicals, or radiation. and the situation: A large amount of radioactive waste was found near the town of Arrester. An unusual number of people in Arrester have cancer. In a town 100 miles north of Arrester named Ajani very few people have cancer. There is no radioactive waste near the town of Ajani Answer the following question: Given a company decides to dump radioactive waste near Ajani, will the chances of developing cancer for the citizens of Ajani increase or decrease?
Ans: increase

Given the background: The stronger of two acids will have a higher Ka than the weaker acid; the ratio of hydrogen ions to acid will be higher for the stronger acid as the stronger acid has a greater tendency to lose its proton. Because the range of possible values for Ka spans many orders of magnitude, a more manageable constant, pKa is more frequently used, where pKa = log10 Ka. Stronger acids have a smaller pKa than weaker acids. Experimentally determined pKa at 25 C in aqueous solution are often quoted in textbooks and reference material. and the situation: Jacob and Thomas were conducting an experiment in a chemistry class. The goal of the experiment was to identify the strength of unknown acids by examining the products formed in a chemical reaction. After they completed the experiment, Jacob concluded that he was given a strong acid, while Thomas concluded that he was given a weak acid. Answer the following question: Which person's acid, Jacob's or Thomas's, will have a larger pKa?
Ans: Thomas's