Atomic Structure and The Periodic Table

• 1. This is the symbol for the element
• 2. Atomic number of the element
• 3. Molar mass or atomic weight

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.

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.

The sum of the neutrons and protons of any element.

Atoms of an element with different numbers of neutrons.

6 Protons 6 Neutrons

6 Protons 8 Neutrons

Horizontal rows on the periodic table

Vertical columns on the periodic table

The position of the electrons in relation to the nucleus.

The shell of an electron that determines the average distance from the nucleus and its energy.

Principal Quantum Number. N=1,2,3...

Have more energy and less stability than electrons in shells with lower values.

This describes the shape of an electrons orbital. s=0 p=1 d=2 f=3

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)

s subshells are spherical while p subshells are dumbbell shaped

• 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)

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

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

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...

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.

• 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)

Elements with all of their electrons SPIN paired. All subshells are complete.

Most elements are paramagnetic because their electrons are NOT spin paired.

Simply put paramagnetic elements are very strongly affected by magnetic fields whereas diamagnetic elements are not as affected.