1. PERIODIC TRENDS
Chapter 6

2. VALENCE ELECTRONS
Electrons in an atom’s highest principle energy level
Valence electrons determine the chemical properties of an element
Atoms in the same group have similar properties because they have the same number of valence electrons
Energy level of valence electrons is indicated by the period in which the element is found

3. IONS Neutral atoms have no overall electrical charge because –
they have equal numbers of positively charged protons in the nucleus and negatively charged electrons surrounding the nucleus.
Noble gases have stable configurations because –
the s and p orbitals of their highest energy level are filled, forming a stable octet.
Exception: helium has only two s e– in its highest energy level

4. IONS Atoms gain or lose electrons to – increase stability by
attaining electron configurations similar to noble gases.
Such an atom is no longer neutral but
has become a charged particle known as an ion.
Metals: lose electrons to become cations (+)
Nonmetals: gain electrons to become anions (–)

5. OXIDATION NUMBERS
Definition: the positive or negative charge of a monatomic ion. It equals the number of electrons transferred when an atom forms its ion.
Predicted by the group of an element
+ when electrons are lost; –when electrons are gained
Written above group number on periodic table
Noble gases have oxidation number of zero: they do not transfer electrons and do not form ions
Elements in carbon group have no oxidation number; they do not typically form ions

6. ATOMIC RADII DECREASES
One half the distance between the nuclei of two adjacent atoms of the same element
Trend across the period (left to right)
Atomic radius DECREASES
Trend within the group (bottom to top)
The General Trend
DECREASES

7. IONIC RADII
One half the distance between the nuclei of two adjacent ions of the same element
Metal atoms tend to ____ electrons to become ______ (________ ions)
Therefore, cations are smaller than their corresponding atoms
Nonmetal atoms tend to ____ electrons to become ______ (________ ions)
Therefore, anions are larger than their corresponding atoms
lose
cations
positive
gain
anions
negative

8. IONIC RADII
One half the distance between the nuclei of two adjacent ions of the same element
Trend across the period (left to right)
Ionic radius DECREASES
Trend within the group (bottom to top)
The General Trend
DECREASES

9. IONIZATION ENERGY INCREASES
The minimum amount of energy required to remove an electron from an atom
Trend across the period
(left to right)
Ionization Energy INCREASES
Trend within the group (bottom to top)
The General Trend
INCREASES

10. ELECTRONEGATIVITY INCREASES
The relative ability of an atom to attract electrons
Trend across the period (left to right)
Electronegativity INCREASES
Trend within the group (bottom to top)
The General Trend
INCREASES

11. REACTIVITY
Refers to how readily chemical substances undergo chemical reaction
Related to several factors, including the number of valence electrons, ionization energy, and electronegativity
Metals: more reactive with low numbers of valence electrons and low ionization energies
Nonmetals: more reactive with larger numbers of valence electrons and high electronegativity values

12. REACTIVITY DECREASES INCREASES
Trend across the period (left to right)
Reactivity of metals DECREASES
Reactivity of nonmetals INCREASES
Trend within the group (bottom to top)
DECREASES
INCREASES