Bio 345 2nd Lecture: Elements, Atoms, and Molecules PDF

Bio 345 2nd lecture ELEMENTS, ATOMS, AND MOLECULES Elements  Living organisms are composed of matter, which is anything that occupies space and has mass (weight)  Matter is composed of chemical elements  Element—a substance that cannot be broken down to other substances  Ther...

Bio 345 2nd lecture ELEMENTS, ATOMS, AND MOLECULES Elements  Living organisms are composed of matter, which is anything that occupies space and has mass (weight)  Matter is composed of chemical elements  Element—a substance that cannot be broken down to other substances  There are 92 elements in nature—only a few exist in a pure state Elements Life requires 25 essential elements; some are called trace elements ‫ال‬that is needed in minute quantities for the proper growth, development, and physiology of the organism. ‫العناصر في جسم األنسان‬ ‫النسبة المئوية‬ ‫العنصر‬ ‫الرمز‬ ‫مـن وزن الجسم‬ ‫‪65.0‬‬ ‫‪O‬‬ ‫األوكسيجين‬ ‫‪18.5‬‬ ‫‪C‬‬ ‫الكربون‬ ‫‪96.3‬‬ ‫‪9.56‬‬ ‫‪H‬‬ ‫الهيدروجين‬ ‫‪3.3‬‬ ‫‪N‬‬ ‫النيتروجين‬ ‫‪1.5‬‬ ‫‪Ca‬‬ ‫الكالسيوم‬ ‫‪1.0‬‬ ‫‪P‬‬ ‫الفوسفور‬ ‫‪0.4‬‬ ‫‪K‬‬ ‫البوتاسيوم‬ ‫‪0.3‬‬ ‫‪S‬‬ ‫الكبريت‬ ‫‪0.2‬‬ ‫‪Na‬‬ ‫الصوديوم‬ ‫‪0.3‬‬ ‫‪Cl‬‬ ‫الكلور‬ ‫‪0.1‬‬ ‫‪Mg‬‬ ‫المغنيسيوم‬ ‫‪ ،(Cr) ،‬الكروميوم )‪(B‬العناصر األثرية ( أقل من ‪ :) %0,01‬البورون‬ ‫‪ ،(Fe) ،‬الحديد )‪ ،(I‬اليود )‪ ،(F‬الفلور )‪ ،(Cu‬النحاس )‪(Co‬الكوبالت‬ ‫‪ ،‬السيليكون )‪ ،(Se‬السيلينيوم )‪ ،(Mo‬الموليبدينيوم )‪(Mn‬المنجنيز‬ ‫‪ ،(Zn).‬الزنك )‪ ،(V‬الفاناديوم )‪ ،(Sn‬التن )‪(Si‬‬  Elements can combine to form compounds  Compound—a substance consisting of two or more different elements combined in a fixed ratio –There are many compounds that consist of only two elements –Table salt (sodium chloride or NaCl) is an example –Sodium is a metal, and chloride is a poisonous gas –However, when chemically combined, an edible compound emerges Elements can combine to form compounds  Many of the compounds in living organisms contain carbon, hydrogen, oxygen, and nitrogen DNA, for example, contains all four of these elements Interestingly, different arrangements of elements provide unique properties for each compound  DNA, for example, contains all four of these elements(carbon, hydrogen, oxygen, and nitrogen ) Elements can combine to form compounds An atom is the smallest unit of matter that still retains the properties of a element Atoms are made of over a hundred subatomic particles, but only three are important for biological compounds - Proton—has a single positive electrical charge - Electron—has a single negative electrical charge - Neutron—is electrically neutral Elements  Elements differ in their number of protons, neutrons, and electrons The number of protons is the atom’s atomic number –-Carbon with 6 protons has an atomic number of 6 –The mass number is the sum of the protons and neutrons in the nucleus (carbon-12 is written 12C) – The number of neutrons in a nucleus affects the mass of the atom but not its chemical properties.  Model of a carbon atom Electron cloud ‫سحابة اليكترونية‬ 6e– Nucleus ‫نواة‬ Protons 6 ‫بروتونات‬ Mass number = 12 12 = ‫الوزن الذري‬ 6 Neutrons ‫نيوترونات‬ 6 Electrons ‫اليكترونات‬ Atoms consist of protons, neutrons, and electrons Neutrons and protons are packed in the atom’s nucleus -The negative charge of electrons and the positive charge of protons keep electrons near the nucleus - The number of protons is the atom’s atomic number - Carbon with 6 protons has an atomic number of 6 - The mass number is the sum of the protons and neutrons in the nucleus (carbon-12 is written 12C)  Atoms consist of protons, neutrons, and electrons  Although all atoms of an element have the same atomic number, some differ in mass number -The variations are isotopes, which have the same numbers of protons and electrons but different numbers of neutrons – -One isotope of carbon has 8 neutrons instead of 6 (written 14C) – Unlike 12C, 14C is an unstable (radioactive) isotope that gives off energy * Radioactive 14Cwas used to show the route of 14CO in formation of sugar during plant 2 photosynthesis  ‫كربون – ‪12‬‬ ‫كربون – ‪13‬‬ ‫كربون – ‪14‬‬ ‫بروتونات‬ ‫نيوترونات‬ ‫إليكترونات‬ isotopes of carbon isotopes of hydrogen The image shows the three isotopes of the element hydrogen. All three forms have one proton (pink) and one electron (dark green) but differ in the number of neutrons (gray) in the nucleus. Portion, or ordinary hydrogen (top), has no neutrons. Deuterium, or hydrogen-2 (bottom left), has one neutron. Tritium, or hydrogen-3 (bottom right), has two neutrons.  Electron arrangement determines the chemical properties of an atom  Only electrons are involved in chemical activity  Electrons occur in energy levels called electron shells Information about the distribution of electrons is found in the periodic table of the elements  ‫‪The electron shell diagrams of the first 18 elements in the periodic table‬‬ ‫أشكال المدارات اإلليكترونية لثمانية عشر عنصرا ً في الجدول الدوري‬ ‫‪Hydrogen‬‬ ‫‪Helium‬‬ ‫الهيدروجين‬ ‫الهيليوم‬ ‫‪First shell‬‬ ‫المدار األول‬ ‫‪Lithium‬‬ ‫‪Beryllium‬‬ ‫‪Boron‬‬ ‫‪Carbon‬‬ ‫‪Nitrogen‬‬ ‫‪Oxygen‬‬ ‫‪Fluorine‬‬ ‫‪Neon‬‬ ‫الليثيوم‬ ‫البيريليوم‬ ‫البورون‬ ‫الكربون‬ ‫النيتروجين‬ ‫األوكسجين‬ ‫الفلور‬ ‫النيون‬ ‫‪Second shell‬‬ ‫المدار الثاني‬ ‫‪Sodium‬‬ ‫‪Magnesium‬‬ ‫‪Aluminum‬‬ ‫‪Silicon‬‬ ‫‪Phosphorus‬‬ ‫‪Sulfur‬‬ ‫‪Chlorine‬‬ ‫‪Argon‬‬ ‫الصوديوم‬ ‫المغنيسيوم‬ ‫االلومونيوم‬ ‫السلسكون‬ ‫الفوسفور‬ ‫الكبريت‬ ‫الكلور‬ ‫األرجون‬ ‫‪Third shell‬‬ ‫المدار الثالث‬ Electron arrangement determines the chemical properties of an atom  An atom may have one, two, or three electron shells –The number of electrons in the outermost shell determines the chemical properties of the atom –The first shell is full with two electrons, whereas the second and third will hold up to eight electrons Electron arrangement determines the chemical properties of an atom  Atoms want to fill their outer electron shells –To accomplish this, the atom can share, donate, or receive electrons –This results in attractions between atoms called chemical bonds