Atoms and Elements Lesson 1 PDF

What are the 11 key systems essential to all living systems? H, O, C, N, Na, K, Ca, Mg, P, S, Cl What elements are found in 99% of the total atoms in the body? H, O, C, N What is matter/atoms mostly made up of? Fundamental particles What three fundamental particles make up atoms? Protons, neu...

What are the 11 key systems essential to all living systems? H, O, C, N, Na, K, Ca, Mg, P, S, Cl What elements are found in 99% of the total atoms in the body? H, O, C, N What is matter/atoms mostly made up of? Fundamental particles What three fundamental particles make up atoms? Protons, neutrons and electrons What is the name of the nucleons found in the atom? Proton and neutron 1 atomic mass unit is.... 1.6605 x10-24 g Charge (C) Mass (amu) ---------- ------------ ------------ ------------- Nucleons Protons +1 1.0073 Neutrons 0 1.0087 Electrons -1 5.4859x10-4 Most of the atom is empty space, the protons and the neutrons are clustered together in the centre to form the nucleus and the electrons from a cloud surrounding this. In atoms there are equal numbers of protons and electrons giving an overall charge of 0. This is a stable atom. If an atom forms with an unstable composition in the nucleus, then it is liable to undergo some form of disintegration. This involves the loss of one or more fundamental particles. This is called radioactive decay. Z Atomic/element number Number of protons in the nucleus (same number as electrons) Defines which element the atom is --- ----------------------- ----------------------------------------------------------------------------------------------- N Neutron number Number of neutrons A Mass number Number of protons and neutrons added Define isotope The same number of protons but different number of neutrons. They have a different A number aswell as N Type of chlorine Stable or unstable In environment ------------------ -------------------- ----------------------------------------------------------------------------------------------------- 35 Stable 75% of Cl in the environment 36 Unstable Undergoes radioactive decay. Has a half-life of 308,000 years negligible amounts in the environment 37 Stable 25% of Cl in the environment Why is 36 Cl unstable but 37 Cl stable? 37 Cl had even number of neutrons to bind the proton together. Binding force more stable. 36 Cl has odd number of neutrons to bind protons together. Therefore binding force unstable. Alpha decay - Emits an alpha particle that has a helium nucleus, 2 protons and 2 neutrons and no electrons. Have a charge of +2. This radition is not very penetrating but high ionising due to large mass can damage tissue. The Z of a molecule decreases by 2 and A decreases by 4. A new element is formed. Beta-minus decay -- A neutron breaks up into a proton and an electron. The electrons is emitted and Z goes up by 1 and A stays the same. Beta-minus decay -- A proton breaks up to a neutron and positron. How does the periodic table list elements in periods (rows)? In order of increasing Z moving from left to right Atomic weight - An average for all the naturally occurring atoms Why do we have an atomic weight? As each element usually occur as more than one isotope How is the weight of each isotope found? By adding the masses of the protons and neutrons only. Why do we not include the weight of the electrons in atomic weight? Electrons are not heavy enough to be significant The atomic numbers for K,Zr,P and Br are the following a. 11,21,39,34 b. 19,40,15,35 c. 37,41,15,35 d. 19,40,50,17 e. 19,40,16,35 Where is the structure of the nucleus important? Radiochemistry and physics What gives atoms their chemical characteristics? Electrons Isotopic labelling can be used to study how an atom is involved in a reaction, metabolic pathway or in a cell. Stable isotopes can be monitored by mass spectrometry, infrared spectroscopy or NMR spectroscopy Radioactive isotopes can be monitored by tracing the radiation emitted e.g PET scan An element is defined by its atomic number. true or false? True If a positive charge attracts negative charges why don't the electrons crash into the nucleus? Due to strong nuclear forces The amount of energy which an electron has determines how far it is from the nucleus Electrons can only be at a certain and specific distances from the nucleus The nucleus was found to be a solid mass of protons and neutrons with a positive charge and the negative electrons were found to surround it The higher up the energy level the greater their potential energy with respect to the ground state Increasing energy levels in atoms are called shells. These are numbered 1,2,3,4 from the lowest energy up. Increasing energy as shell number increases As shells become larger, they can hold more electrons. True or false? True More shielding decreases nuclear attraction. Easier to remove outer electron due to repulsive forces Why does a lower nuclear attraction easier to remove outer electrons? Electrons are less attractive to protons in the nucleus Electrons in the higher energy shells, less close to the nucleus and its positive attraction are held less strongly in the atom To move an electron to a higher energy level shell it has been shown that a specific amount of energy is required. When an atom absorbs energy, the electron moves to a higher energy level excited state The amount of energy required to move an electron to a higher energy level is called quanta Electrons jumping down to a lower energy shell will emit a quantum of energy. A photon is emitted when an electrons moves from a higher energy level to a lower energy level. The energy of the emitted photon is equal to the difference in energy between the energy levels in the transition. The ground state is the lowest energy level possible. Rhodopsin will absorb light and an electron in the coupled 11-cis-retinal is excited to a higher energy level excited to a higher energy level, triggering a series of reactions that send an electrical signal to the brain. Energy only comes in fixed amounts or quanta Sub-atomic particles have wave-like and particle-like properties The uncertainty principle and wave equations meaning when applied to electrons -- We cannot know both position and speed of a particle such as a photon or electron with perfect accuracy. We can only say where the greatest probability to find them. Shells can be further divided into orbitals, each of which contain two electrons. Orbitals are characterised bby the shape produced when the region surrounding the nucleus is plotted in which there is a 95% chance of finding the electrons S and p orbitals are involved in the bonding of atoms S orbitals are the simplest orbital which is a sphere 1s is an s orbital in shell 1 and 2s is and orbital in shell 2 Each s-orbital only contains 2 orbitals The orbital sphere increases as the energy level or shell increases Shell 1 contains only the 1s orbital and contains only 2 electrons P orbitals are more complex than s and have a dumbbell shape and come in 3 different types 2py,2px and 2pz Each axis p-orbital can only accommodate 2 electrons each making a total of 6 electrons. Adding this to the 2 electrons in s orbital creates a total of 8 electrons Shell 2 contains 2s orbital containing 2 electrons and three 2 p orbitals containing 6 orbitals One spherical s orbital and 3 p orbitals each with 2 lobes pointing along the x, y and z axes in the second energy level D orbitals have more complex shapes than P and the lowest energy shell containg d orbitals is n=3 Transition metals have a d-orbital which have a variable oxidation state. Degeneracy -- If two or more orbitals have the same energy and same distance from the nucleus, they are degenerate.