Atomic Structure Chemical Bonding And Chemical

SCH 102Atomic StructureChemical BondingandChemical StructureDr. Solomon Derese50

SCH 102Atomic StructureDr. Solomon Derese51

AtomsSCH 102The basic building block of all matter is called anatom.Atoms are a collection of various subatomic particlescontaining negatively charged electrons, positivelycharged protons and neutral particles calledneutrons.Each element has its own unique number ofprotons, neutrons and electrons. Both protons andneutrons have mass, whereas the mass of electronsis negligible.Dr. Solomon Derese52

SCH 102The three fundamental subatomic particles of anatom are electrons, protons and neutrons.ParticleActual mass(kg)Proton, p 1.6726 10-27Neutron, n 1.6749 10-27RelativeChargemasscharge(Coulomb)(amu)1.007 1.6022 10-19 11.00800Electron, e- 9.1094 10-31 5.489 10-4 -1.6022 10-19mass p mass n 1840 mass-1eProtons and neutrons exist at the centre of the atomin the nucleus.Dr. Solomon Derese53

SCH 102It is important to understand the location ofelectrons, as it is the arrangement of the electronsthat creates the bonds between the atoms. Electronsare involved in the chemical bonding and reactions ofan atom.Electrons move around the nucleus, and are arrangedin shells at increasing distances from the nucleus.These shells represent different energy levels, theoutermost shell being the highest energy level.Electrons do not move freely in the space around thenucleus but are confined to regions of space calledshells.Dr. Solomon Derese54

SCH 102Model of an atom3shell21pnnucleusp protonsDr. Solomon Deresen neutrons electrons55

SCH 102Each shell can contain up to a maximum of 2n2electrons, where n is the number of the shell. For thefirst shell n 1, for the second shell n 2, for the thirdshell n 3 and so on.Low energyShell123High energy 4Dr. Solomon DereseMaximum number of electrons28183256

SCH 102Each shell contains subshells known as atomicorbitals.Electrons are said to occupy orbitals in an atom. Anorbital can hold two electrons.The different orbitals are s, p, d and f.Subshell # of orbitals ofequal energys1p3d5f7Dr. Solomon DereseMaximum # ofelectrons26101457

SCH 102Each shell contains subshells known as atomicorbitals.Shell123Dr. Solomon DereseSubshells and Orbitals1s2s and 2P (px, py and pz)3s and 3P (px, py and pz) and five 3 d58

Electronic ConfigurationSCH 102The electronic configuration of an atomdescribes the number of electrons that anatom possesses, and the orbitals in whichthese electrons are placed.The arrangements of electrons in orbitals,subshells and shells are called electronicconfigurations.Dr. Solomon Derese59

Building up of electronic 146s2p6d10f147s2p6d10f14Dr. Solomon DereseSCH 10260

SCH 102Rules of Filling Electron OrbitalsAufbau Principle:Electrons are added one at a time to the lowestenergy orbitals available until all the electrons ofthe atom have been accounted for.Pauli Exclusion Principle:An orbital can hold a maximum of two electrons.To occupy the same orbital, two electrons mustspin in opposite directions.Hund’s Rule:Electrons occupy equal-energy orbitals so that amaximum number of unpaired electrons results.Dr. Solomon Derese61

SCH 102ElementElectron Configuration1s1H2He3Li6C7N8O9F10Ne11NaDr. Solomon DereseOrbital Filling2s2px 2py 51s22s22p61s22s22p63s162

Chemical Bonding and Chemical Structure. SCH 102 Dr. Solomon Derese 51 Atomic Structure. SCH 102 Dr. Solomon Derese Atoms The basic building block of all matter is called an atom. Each element has its own unique number of protons, neutrons and electrons. Both protons and