An overview of important concepts of the periodic table and atomic structure.
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 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.
Principal Quantum Number
The shell of an electron that determines the average distance from the nucleus and its energy.
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
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.
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
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.
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.
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.