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ELECTRON ORBITALS. Electron Configuration. Definition: the process of arranging electron in an atom around the nucleus. Remember: for a neutral atom, the # of protons is equal to the # of electrons. The path along which electrons move round the nucleus is called the orbital or shell
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Electron Configuration • Definition: the process of arranging electron in an atom around the nucleus. • Remember: for a neutral atom, the # of protons is equal to the # of electrons. • The path along which electrons move round the nucleus is called the orbital or shell • These orbital are arranged in energy levels. Electrons with less energy are closer to the nucleus. • The energy levels are labeled from inside outwards. • 1st energy level can hold only up to 2 electrons, 2nd and 3rd energy levels can hold up to 8 electrons each. 4th energy level can hold up to 18 electrons
Electron Energy Level (Shell) Generally symbolized by n, it denotes the probable distance of the electron from the nucleus. “n” is also known as the Principle Quantum number Number of electrons that can fit in a shell: 2n2
Electron configuration cont. 4 3 Orbital 2 1 e e + e ++ + e Protons e e e e e e e e e +++++++++++++++ e e ++++++++ e e e e e e e e e e Electrons e
Definition: Outermost electrons on an atom. • Uses of valence electrons • Determines the group to which an elements is place on the periodic table • Used or are available for bonding Valence Electrons e e e ++++++ Valence electrons e e e Atomic # 6
Elements are arranged from left to right by increasing atomic # and (by increasing atomic mass!) • The periodic table has 18 columns called groups • Each group number (1, 2, 13, 14, 15, 16, 17, 18) in red represents # of valence electrons • It also has 7 rows called periods • Each row number represents # of orbital (Row 1 can have only 2 elements) • Arrange the 1st 20 elements into 8 columns and 4 rows. What do elements of each column has in common? What do elements in each row have in common? Arranging Elements on the periodic table
Arranging elements on the periodic table cont. Groups 1 18 1 2 13 14 15 16 17 He 2 3 3 4 5 6 7 8 9 10 11 12 4 Periods 5 6 7
Standard 1c. Students know how to use the periodic table to identify alkali metals, alkaline earth metals and transition metals, Noble gases; trends in ionization energy, electronegativity, and the relative sizes of ions and atoms.
Names given to certain groups of the periodic table Noble gases Alkali metal Alkaline Earth metal Halogens Transition metals 1 18 2 13 14 15 16 17 3 4 5 6 7 8 9 10 11 12
Elements on the periodic table are classified as: • Metals • Semi metals or metalloids • Non-metals • Use the periodic table to hi-light: metals; semi metals; and non-metals. • Using the periodic table, classify the following elements as metal, metalloid, or non-metal • 1st 20 elements, Cu, Pb, Xe, Ar, Ge, I, Ba, Bi,& Sb. Classifying elements on the periodic table
Definitions: Ionization energy – energy required to remove an electron from an atom Electronegativity – ability for an atom to attract an electron Atomic size – distance from the nucleus to the farthest electron. Cation – an atom that has loss one or more electrons (an atom that has more protons than electrons) Anion – an atom that has gained one or electrons (an atom that has more electrons that protons) Trends (patterns) of some properties exhibited by elements on the periodic table
Trends (patterns) cont. • 2 factors that account for all the trends on the periodic table include: • As we move from left to right in a periodic table, electrons are added one a time. The outermost shell hence experiences increased nuclear attraction and hence electrons are more bound to the nucleus. • When moving from top to bottom in the column of periodic table of elements, valence electrons experience less nuclear attraction. The reason being that going down the periodic table, the number of principal energy levels increases and hence attraction decreases.
Summary of Periodic Table Trends Moving Left to Right • Atomic Radius Decreases • Ionization Energy Increases • Electronegativity Increases Moving Top to Bottom • Atomic Radius Increases • Ionization Energy Decreases • Electronegativity Decreases Trends in Ionization energy; Electronegataivity and Atomic size • Draw graphs of • Atomic size Vs Atomic # • Ionization energy vs • Atomic # • 3. Electronegativityvs • Atomic #
1st known periodic table of elements was arranged by John Newlands in order of increasing atomic mass. The next table was by Dmitri Mendeleev. He also arranged the elements in order of increasing atomic mass. But his table was different in that He left gaps for undiscovered elements, He interchange elements that fall in the wrong group even though they have higher atomic mass. Henry Moseley arranged his table in order of increasing atomic number. (our present day period table) Brief History of the periodic table
Definition of words • Alkali metal; all elements of group 1, except Hydrogen. • Alkaline earth metal: all elements of group 2. • Transition metals: all elements of group 3 thro’ 12. • Noble gases: all non-metals of group 18. They have full valence shells or orbital. • Electronegativity: ability of a bonded element to attract bonded electrons. • Ionization energy: energy required to remove electrons from an atom • Atomic size: size of the atom usually measured by the radius of the atom. • Ion: atom that has either gained or loss an electron. • Activity: using the periodic table provided and using different colors, indicate alkali metal; alkaline earth metals; Transition metals and Noble gases. All the trend.
