Periodicity: the arrangement of the chemical elements in the Periodic Table allows for the
prediction of their properties following a trend by either groups or periods
Group number: related to the electrons in the valence shell
Period number: highest main energy level with electrons
**Groups 3 and 12 are part of the d-block elements; they are not transition metals
**F-block elements are periods 6 (lanthanides) and 7 (actinides)
Effective nuclear charge (ENC): is the net attraction of the protons on the electrons of a given
shell
- NC - nuclear charge: number of protons in a nucleus
Distance nucleus-valence electrons: The bigger the atom, lower attraction between the protons
and the valence electrons
First ionization energy: minimum energy required to remove 1 mole of electrons from 1 mole
of neutral gaseous atoms to form 1 mole of gaseous 1+ ions.
- Trend: decreases down a group due to the atom growing in size and thus the distance
getting weaker; increases across a period because the atoms have 1 more proton so the
attraction increases within the atom.
- Q (g) → Q+ (g) + electron
- Units: kJ/mol
- Exceptions B/Be and N/O due to the stability of the configuration
Electronegativity: measure of the attraction of an atom for the electrons shared in a covalent
bond
- Pauling’s scale: 0 (noble gasses) to 4 (fluorine)
- Trend: decreases down a group due to the atom growing in size and thus the distance
getting weaker; increases across a period because the atoms have 1 more proton so the
attraction increases within the atom.
Atomic radius: how large the atom is
- Trend: increases down a group as the atom has more energy levels; decreases across a
period as the atoms have the same number of energy levels but the number of protons
increases which means there is a higher ENC pull the shells together
Ionic radius:
, - Positive ions are smaller than the neutral atom as they have less energy levels
- If making a cation does not empty an energy level the reason for it to be smaller is
due to the decrease in electron repulsion present
- Negative ions are bigger than the neutral atom as the electron repulsion increases
Isoelectronic species: some ions that have the same number of electrons
- More protons = smaller as there is more attraction
- Na+ < Ne < F- they all have the same number of electrons however they are ranked in
order of decreasing protons
Electron affinity: energy associated with the gaining of 1 electron
- Na (g) + electron → Na- (g)
- Units: kJ/mol
- Trend: it increases up a group as there is more attraction from the nucleus; increases
across a period as the ENC increases.
Alkali metals: elements that are the most metallic which means they lose electrons more readily
(they oxidize)
- Metallic character increases down a group and decreases across a period
- Characteristics
- The more metallic an element is the more reactive it is (chemical)
- They have low density (physical)
- Easily oxidized (chemical)
- They are soft (physical)
- They are shiny → when cut they are dull (physical)
- Reaction in water → exothermic (there is a release of energy to the environment from the
system)
- Li (s) + H2O (l) → LiOH (aq) + ½ H2 (g)
- Li - fizzes (produces bubbles); Na - catch fire; K - explode; it gets worse
Halogens: In each period the halogen is the most reactive nonmetal; they gain electrons more
easily (they reduce)
- Reactivity increases up a group and increases across a period
- Characteristics
prediction of their properties following a trend by either groups or periods
Group number: related to the electrons in the valence shell
Period number: highest main energy level with electrons
**Groups 3 and 12 are part of the d-block elements; they are not transition metals
**F-block elements are periods 6 (lanthanides) and 7 (actinides)
Effective nuclear charge (ENC): is the net attraction of the protons on the electrons of a given
shell
- NC - nuclear charge: number of protons in a nucleus
Distance nucleus-valence electrons: The bigger the atom, lower attraction between the protons
and the valence electrons
First ionization energy: minimum energy required to remove 1 mole of electrons from 1 mole
of neutral gaseous atoms to form 1 mole of gaseous 1+ ions.
- Trend: decreases down a group due to the atom growing in size and thus the distance
getting weaker; increases across a period because the atoms have 1 more proton so the
attraction increases within the atom.
- Q (g) → Q+ (g) + electron
- Units: kJ/mol
- Exceptions B/Be and N/O due to the stability of the configuration
Electronegativity: measure of the attraction of an atom for the electrons shared in a covalent
bond
- Pauling’s scale: 0 (noble gasses) to 4 (fluorine)
- Trend: decreases down a group due to the atom growing in size and thus the distance
getting weaker; increases across a period because the atoms have 1 more proton so the
attraction increases within the atom.
Atomic radius: how large the atom is
- Trend: increases down a group as the atom has more energy levels; decreases across a
period as the atoms have the same number of energy levels but the number of protons
increases which means there is a higher ENC pull the shells together
Ionic radius:
, - Positive ions are smaller than the neutral atom as they have less energy levels
- If making a cation does not empty an energy level the reason for it to be smaller is
due to the decrease in electron repulsion present
- Negative ions are bigger than the neutral atom as the electron repulsion increases
Isoelectronic species: some ions that have the same number of electrons
- More protons = smaller as there is more attraction
- Na+ < Ne < F- they all have the same number of electrons however they are ranked in
order of decreasing protons
Electron affinity: energy associated with the gaining of 1 electron
- Na (g) + electron → Na- (g)
- Units: kJ/mol
- Trend: it increases up a group as there is more attraction from the nucleus; increases
across a period as the ENC increases.
Alkali metals: elements that are the most metallic which means they lose electrons more readily
(they oxidize)
- Metallic character increases down a group and decreases across a period
- Characteristics
- The more metallic an element is the more reactive it is (chemical)
- They have low density (physical)
- Easily oxidized (chemical)
- They are soft (physical)
- They are shiny → when cut they are dull (physical)
- Reaction in water → exothermic (there is a release of energy to the environment from the
system)
- Li (s) + H2O (l) → LiOH (aq) + ½ H2 (g)
- Li - fizzes (produces bubbles); Na - catch fire; K - explode; it gets worse
Halogens: In each period the halogen is the most reactive nonmetal; they gain electrons more
easily (they reduce)
- Reactivity increases up a group and increases across a period
- Characteristics
