# Atomic Structure and The Periodic Table 1. What does the 'C' stand for ? 2. What does the '6' stand for? 3. What does '12.01' mean? 1. This is the symbol for the element2. Atomic number of the element3. Molar mass or atomic weight Atomic Number The atomic number is the same as the number of protons in the nucleus of an element. It is also the same as the number of electrons surrounding the nucleus in its ground state. The number is normally found above the symbol of the element on the periodic table. Molar mass Mass of one mole of a substance. Sometimes called atomic weight, and is usually found below the symbol on the periodic table. Usually in the units g/mol. Average of the mass numbers of all known isotopes weighted by their percent abundance. Mass Number The sum of the neutrons and protons of any element. Isotopes Atoms of an element with different numbers of neutrons. Carbon-12 6 Protons 6 Neutrons Carbon-14 6 Protons 8 Neutrons Periods Horizontal rows on the periodic table Group Vertical columns on the periodic table Quantum numbers The position of the electrons in relation to the nucleus. Principal Quantum Number The shell of an electron that determines the average distance from the nucleus and its energy. Shell Principal Quantum Number. N=1,2,3... Electrons that are farther away from the nucleus will... Have more energy and less stability than electrons in shells with lower values. The Angular Momentum Quantum Number This describes the shape of an electrons orbital. s=0 p=1 d=2 f=3 Subshell The Angular Momentum Quantum Number. L=0,1,2,3... -The first shell (n=1) has one subshell: s, or l=0-The second shell (n=2) has two subshells: s (l=0) and p(l=1)- The third shell (n=3) has three subshells; s (l=0) p (l=1) and d (l=2) What are the shapes of the orbitals of the s and p subshells? s subshells are spherical while p subshells are dumbbell shaped The Magnetic Quantum Number This is often referred to as the orbital. s (0) p (-1) (0) (1) d (-2) (-1) (0) (1) (2) f (-3) (-2) (-1) (0) (1) (2) (3) Orbitals The Magenetic Quantum Number. M sub l= -1,0,1 -The s subshell (l=0) has one orbital M sub l=0-The p subshell has three orbitals M sub l= -1,0,1-The d subshell has five orbitals M sub l= -2,-1,0,1,2 The Spin Quantum Number Each orbital can contain two electrons: one with a positive spin and one with a negative spin. -M sub s = +1/2 or -1/2 The Aufbau Principle This states that when building up the electron configuration of an atom, electrons are placed in orbitals, subshells, and shells in order of increasing energy. As in 1s2 2s2 2p6 3s2... The Pauli Exclusion Principle States that within an atom, no two electrons can have the same set of quantum numbers. So, each electron in any atom has its own distinct set of quantum numbers. Hunds Rule Electrons, when added to a subshell, will always occupy an empty orbital if one is available. Electrons always occupy orbitals singly if possible and pair up only if no empty orbitals are available. -Boron 1s (11) 2s (11) 2p (1) () ()-Carbon 1s (11) 2s (11) 2p (1) (1) () -Nitrogen 1s (11) 2s (11) 2p (1) (1) (1) - Oxygen 1s (11) 2s (11) 2p (11) (1) (1) Diamagnetism Elements with all of their electrons SPIN paired. All subshells are complete. Paramagnetism Most elements are paramagnetic because their electrons are NOT spin paired. Are paramagnetic or diamagnetic elements more affected by magnetic fields? Simply put paramagnetic elements are very strongly affected by magnetic fields whereas diamagnetic elements are not as affected. AuthorAnonymous ID27625 Card SetAtomic Structure and The Periodic Table DescriptionAn overview of important concepts of the periodic table and atomic structure. Updated2010-07-22T04:15:47Z Show Answers