Chapter 2 (Atomic Structure) Lecture Notes PDF

 College of Biotechnology General Chemistry Lecture 2 Atoms, Ions and Molecules Dr. M. Abd-Elhakeem Composition of Matter Matter - Everything in universe is composed of matter Matter is anything that occupies space or has...

 College of Biotechnology General Chemistry Lecture 2 Atoms, Ions and Molecules Dr. M. Abd-Elhakeem Composition of Matter Matter - Everything in universe is composed of matter Matter is anything that occupies space or has mass Mass – quantity of matter an object has Weight – pull of gravity on an Elements Pure substances that cannot be broken down chemically into simpler kinds of matter More than 100 elements Compounds Most elements do not exist by themselve s Readily combine with other elements in a predictabl e fashion  A compound is a pure substance made up of atoms of two or more elements The proportion of atoms are always fixed Atoms The simplest particle of an element that retains all the properties of that element Properties of atoms determine the structure and properties of the matter they compose Our understanding of the structure of atoms based on scientific The Nucleus Central core Consists of positive charged protons and neutral neutrons Positively charged Contains most of the mass of the atom  The Protons All atoms of an element have the same number of protons Number of protons balanced by an equal number of negatively charged electrons The Neutrons The number varies slightly among atoms of the same element Neutrons are neutral charged The Electrons Negatively charged high energy particles with little or no mass Travel at very high speeds at various distances (energy levels) from the nucleus Electronic configuration  Energy Levels Atoms have 7 energy levels The levels are K (closest to the nucleus), L, M, N, O, P, Q (furthest from the nucleus) The K level can only hold 2 electrons Levels L can hold 8 electrons  Electrons in the same energy level are approximately the same distance from the nucleus Outer energy levels have more energy than inner levels  Sub shell (atomic orbital) Each shell is composed of one or more subshells, which are themselves composed of atomic orbitals. For example, the first (K) shell has one subshell, called "1s"; the second (L) shell has two subshells, called "2s" and "2p"; the third shell has "3s", "3p", and "3d"; and so on  s orbital has spherical form p orbital is composed of three degenerate dumbbell-shaped orbitals px, py, pz d orbital is composed of five degenerate orbitals f is composed of seven degenerate orbitals Each orbital is occupied with 2 electrons  Maximum number of electrons in each subshell: s=2, p=6, d=10, f=14 Order for filling subshells: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p where the number indicates the energy level and the letter indicates the subshell being filled