Atom Midterm

ATOM  Atom is the building block of matter. It came from the Greek word “atomos” which means indivisible. ELECTRON PROTON NEUTRON EUGEN JAMES DISCOVERER JJ THOMSON GOLDSTEIN...

ATOM  Atom is the building block of matter. It came from the Greek word “atomos” which means indivisible. ELECTRON PROTON NEUTRON EUGEN JAMES DISCOVERER JJ THOMSON GOLDSTEIN CHADWICK CHARGE NEGATIVE POSITIVE NEUTRAL OUTSIDE THE INSIDE THE INSIDE THE LOCATION NUCLEUS NUCLEUS NUCLEUS ORBITAL – region where there is a high probability of finding an electron in an atom  JOHN DALTON – an English Chemist who developed the first modern atomic theory where he theorized atom as the smallest particle of elements and molecules as the smallest particle of compound.  ATOMIC THEORY All matter are composed of tiny indivisible particles called atoms. All atoms of a given substance are identical but different from the atoms of other substances. Compound is a combination of two or more type of atoms. It combines in a fixed ratio of small whole numbers to form compounds. Chemical reaction rearranges atoms. Atoms are permanent and cannot be decomposed. DEVELOPMENT OF THE ATOMIC MODEL  JJ THOMSON’S PLUM PUDDING MODEL In 1889 after the discovery of electron and proton, JJ Thomson suggested an atomic model composed of a sphere of positive particles with embedded electrons. His model can be called “Plum pudding model”. Negatively-charged electrons (raisins) are surrounded by a positively charged pudding.  ERNEST RUTHERFORD’S NUCLEAR MODEL In 1911, Ernest Rutherford used the gold foil experiment and concluded after that: Atom consists of large empty space. Atom has a very small region which is later named as nucleus. Nucleus is positively charged. Negatively charged electrons surround the nucleus of an atom. The electrons revolve around the nucleus following a circular path called orbital.  NIELS BOHR SOLAR SYSTEM MODEL Solar system is a model proposed in 1912 where electrons are moving in definite energy levels. The electrons are characterized by a definite amount of energy and remain in the energy level  MAIN FEATURES OF BOHR’S MODEL 1.As the principal quantum number(n) increases, the orbits (shells) radius increases. 2.Electrons in n=1 orbit/shell have the lowest energy. As the value of n increases, the energy of the electron increases. 3.Each orbit/shell can hold a maximum of 2n² electrons. n =1 = 2(1²) = 2 electrons n =2 = 2(2²) = 8 electrons A. MAIN ENERGY LEVELS OR SHELLS the orbits in which the electrons revolve and designated by numbers 1,2,3,4,5 or letter K,L,M,N,O = 2n² Main energy levels are consist of each principal quantum number (n) and orbit/shell consists of subshells. The principal quantum n tells the number of subshells. ○ n=1 has 1 subshell ( s ) ○ n=2 has 2 subshells ( s, p ) ○ n=3 has 3 subshells ( s , p, d ) ○ n = 4 has 4 subshells ( s , p, d, f ) B. SUBLEVELS OR SUBSHELLS ○ s – sharp (max. number of 2 electrons) ○ p – principal (max. number of 6 electrons) ○ d – diffuse (max. number of 10 electrons) ○ f – fundamental (max. number of 14 electrons)  EQUALLL # OF PROTONS = ATOMIC NUMBER # OF ELECTRONS = ATOMIC NUMBER # OF NEUTRONS = ATOMIC MASS – # OF PROTONS  ELECTRON CONFIGURATION  WHAT IS ELECTRON CONFIGURATION? Electron configuration is the arrangement of electrons orbiting the nucleus. Abbreviated configuration uses noble/inert gases (Group 8) to present a shorter configuration of an electron structure. ELECTRON CONFIGURATION Subshell Electrons s 2 p 6 d 10 f 14 AUFBAU METHOD means “building up” suggested by Wolfgang Pauli In arranging the electrons, the energy levels with the lowest energy are filled to the capacity before going to the next energy level.  ELECTRON CONFIGURATION AND SUBLEVELS ORBITAL ORBITAL DIAGRAM s 1 In making an orbital p 3 diagram, Hund’s rule is d 5 used. f 7 In HUND’S RULE OF MULTIPLICITY, it specifies that within a given sublevel, one electron should be placed in each orbital before pairing could occur. QUANTUM NUMBERS  QUANTUM NUMBERS These are the parameters used to describe the electron of an atom. HEISENBERG UNCERTAINTY PRINCIPLE - It is impossible to determine accurately both the momentum and position of a particle simultaneously. PAULI’S EXCLUSION PRINCIPLE - No two electrons of an atom will have the same set of quantum numbers.  FOUR QUANTUM NUMBERS 1. PRINCIPAL (n) – specifies the energy of an electron and the size of its orbital. It defines the total energy of the electron. It has a value of 1-7. 2. AZIMUTHAL (l) – designates the sublevel and measures the angular momentum of the electron. It specifies the shape of an orbital. The values range from 0 to 3. 3. MAGNETIC (m) –determines the number of orbitals and its orientation within a subshell. The values of m, are from –l through 0 to l. 4. SPIN (s) – describes the electron spin within an orbital (either spin up or spin down) Clockwise (+) + 1/2 Counter clockwise (-) -1/2  VALENCE ELECTRONS VALENCE ELECTRONS Valence electrons are the electrons in the outer energy level of an atom that participate in atoms interaction. These are the electrons that are farthest from the nucleus and result to the attraction to another atom than their own nucleus. ELECTRON DOT NOTATION Simple diagram that show only the valence electrons of an element. The symbol for an element is used to represent the nucleus and all inner electrons while a dot is used for each of the valence electrons. PREPARED BY: ANN KIMBERLY S. MENDOZA General Education Department