AP Biology|Complete Questions with A+ Graded Answers

AP Biology|Complete Questions with A+ Graded Answers Elements Elements are substances that cannot be broken down into simpler substances by chemical means. Oxygen Oxygen is an element with symbol O and atomic number 8. It is a highly reactive nonmetal and oxidizing agent. In living organisms, oxygen is used in respiration and in a number of organic molecules. Carbon Carbon is an non mental element with symbol O and atomic number 6. It is the second most abundant element in living organisms and is present in all organic compounds. Hydrogen Hydrogen is an element with symbol H and atomic number 1. Hydrogen combines with non-metallic elements to form water and other organic compounds. Nitrogen Nitrogen is an element with the symbol N and atomic number 7. In biology, nitrogen is important as it is found in a number of organic compounds and is used in fertilizers and antibiotics. Trace elements Trace elements are elements required by an organism in very small quantities. Trace elements include iron, iodine, and copper. Atom An atom is the smallest unit of an element that retains its characteristic properties; they are the building blocks of the physical world. Protons Protons are positively charged subatomic particles that are found in an atom's nucleus. Neutrons Neutrons are uncharged subatomic particles found in an atom's nucleus. Electrons Electrons are negatively charged subatomic particles that spin around the nucleus. Nucleus The nucleus is the positively charged core in an atom made up of neutrons and protons. Isotopes Atoms that have the same number of protons but differ in the number of neutrons in the nucleus are called isotopes.