Atomic Structureand thePeriodic Table

Basics of Periodic Table Each box on the table represents an

element. In each box…

an element symbol the element’s atomic number the element’s average atomic mass

Elements arranged in order of increasing atomic number.

Isotope symbol (neutral)Mass number(#p + #n)

Atomic number(#P)

Isotope name

C146

Isotope symbol (charged)

23416S

Average Atomic Mass The masses found on the periodic

table are called average atomic masses.

They represent the weighted average of all the isotopes found in a sample of the element Isotopes are atoms of the same element

with different numbers of neutrons

ExampleThe atomic masses of the two stable isotopes of

boron, boron-10 (19.78%) and boron-11 (80.22 %), are 10.0129 amu and 11.0093 amu, respectively. Calculate the average atomic mass of boron.

Remember… Electron configuration…ie. Shorthand

Should be able to do shorthand w/o diagonal rule Aufbau principle – electrons fill energy levels

and sublevels in order of increasing energy Pauli Exclusion principle – no two electrons can

have the same set of four quantum numbers (which means no two electrons can be in the same place at the same time

Hund’s rule – when adding electrons to sublevels with more than one orbital, each orbital gets its own electron first before pairing

s orbitals

p orbitals

d orbitals

f orbitals

Quantum Numbers Just as a point on an xy-graph needs a

set of two coordinates, each electron has a unique set of four coordinates.

These four coordinates represent shell (energy level), subshell (sublevel), orbital, and spin direction of the electron.

Principal Quantum number

Represented by n Corresponds to the rows of the

periodic table Therefore n = 1, 2, 3, and so on Tells the size of the electron cloud

2nd Quantum number Represented by l Called the angular momentum quantum

number Describes the shape of the orbital l can have the values from 0 to n-1

0 = s sublevel 1 = p sublevel 2 = d sublevel 3 = f sublevel

3rd Quantum Number Called the magnetic quantum number Describes the orientation in space of the orbital

Whether the path of the electron lies on the x, y, or z axis

Represented by ml

ml can have values from –l to +l if l = 2, then ml = -2, -1, 0, +1, +2

4th Quantum Number Corresponds to the spin of an

electron Represented by ms

Clockwise represented by +1/2 Counterclockwise represented by -

1/2

Therefore Mg (3, 0, 0, -1/2)

Bi (6, 1, +1, +1/2)

Co (3, 2, -1, -1/2)

Cf (5, 3, -1, -1/2)

Diamagnetism/Paramagnetism Diamagnetic elements have all of

their electrons spin paired. Which means they have complete

sublevels. Are not affected by a magnetic field

Paramagnetic elements do not have all of their electrons spin paired. Strongly affected by a magnetic field

Ground State vs Excited State In a ground state atom, all electrons are

in the lowest available sublevels.

For an atom in the excited state, one or more electrons have absorbed enough energy to jump to higher energy levels. As soon as possible, those excited electrons

will release the energy in the form of a photon, possibly as colored light.

Shorthand for ionsCa2+ 1s22s22p63s23p6

K+ 1s22s22p63s23p6

Cl- 1s22s22p63s23p6

S2- 1s22s22p63s23p6

P3- 1s22s22p63s23p6

All of these ions have the same configuration as argon and are isoelectronic.