Kỳ thi SAT gồm 3 phần chính: Toán, Đọc hiểu và Viết bài luận, thang điểm cho mỗi phần từ 200 đến 800 điểm. Điểm SAT là tổng điểm của 3 phần cộng lại. Thời gian thi là 3 giờ 45 phút, không tính thời gian nghỉ. Bạn có thể chuẩn bị cho kỳ thi SAT khi đang học lớp 9,10,11 hoặc 12, và chuẩn bị càng sớm, cơ hội đạt điểm cao sẽ càng lớn. Phần khó nhất đối với người luyện thi SAT là phần Đọc và Viết. Hai phần này đòi hỏi người học có trí nhớ tốt. | CHEMISTRY ATOMS AND COMPOUNDS statistical statement placing it somewhere in a cloud surrounding the nucleus depending on its energy state. C. Atomic Number The number of protons in an atom. D. Atomic Mass The number of protons and neutrons in the nucleus of an atom. Electrons are not considered in this number. The actual number on the periodic table is an average of the abundance of all the isotopes of each element. Carbon-12 Carbon-14 Isotopes of Carbon E. Isotope Different form of an atom due to a different number of neutrons. Carbon 12 has six neutrons while Carbon 14 has eight neutrons. Different isotopes of an element have slightly different properties that are sometimes biologically important. Formation of Ions F. Ion Electrically charged atom due to a loss 1 ion or gain - ion of electrons. An ionic bond is an attractive force of oppositely charged ions by virtue of the loss gain of electrons that takes place between them. As atoms lose electrons and thus become positive attraction occurs with the atoms that gain electrons and thus become negative. Peterson s SAT II Success Biology E M 37 CHAPTER 1 Some essential atoms A. Hydrogen Simplest element that has one proton and one neutron. It combines with oxygen to form water an essential abiotic substance for living things. Hydrogen Carbon Nitrogen Oxygen Phosphorus Sulfur Atoms of Life B. Carbon Ubiquitous element on this planet that forms the basis for all living things. It can form the most number of bonds in chemical combinations. C. Nitrogen Essential component of proteins and nucleic acids. D. Oxygen Necessary for aerobic respiration to take place and in the formation of many organic molecules. E. Phosphorous Necessary for nucleic acid structure and in energy transformations. Also important in membrane structure. F. Sulfur Forms sulfide bridges that are found in proteins. Peterson s SAT II Success Biology E M ặặj CHEMISTRY ATOMS AND COMPOUNDS Methane molecule Molecules .
