1
CHAPTER 2: THE PERIODIC TABLE
(2.1) THE PERIODIC TABLE
● Periodic Table of the Elements → 1st published by Dmitri Mendeleev (a Russian chemist) in
1869
↳ Showed that ordering the known elements by atomic weight revealed a pattern of
periodically recurring physical & chemical properties
○ Has since been revised to organize elements based on increasing atomic number
instead (with work of English physicist Henry Moseley)
○ Creates a visual representation of the periodic law: “The chemical & physical
properties of the elements are dependent, in a periodic way, upon their atomic
numbers.”
● PT arranges elements into periods (rows) & groups/families (columns) – based on atomic
number
○ There are 7 periods representing the principal quantum numbers: n = 1 → n = 7
■ Each period is filled sequentially
■ Each element in a given period has 1 more proton & 1 more electron than
the element to its left (in their neutral states)
○ Groups → contain elements with the same electron configuration in their valence
shell + share similar chemical properties
● Valence electrons: the electrons in the valence shell
○ Farthest from nucleus & have the greatest amount of potential energy
○ Able to become involved in chemical bonds with valence electrons of other atoms →
largely determine chemical reactivity & properties of the element
● The Roman numeral above each group = the number of valence electrons elements in that
group have in their neutral state
○ NOTE: Roman numerals 1-10:
1. I
2. II
3. III
4. IV
5. V
6. VI
7. VII
8. VIII
, 2
9. IX
10. X
○ Roman numeral is combined with letter A or B to separate the elements into 2
larger classes:
1. A elements A.K.A. representative elements → include groups IA → VIIIA
↳ These elements have their valence electrons in the orbitals of either s
or p subshells
2. B elements A.K.A. nonrepresentative elements → include both the transition
elements (have valence electrons in s & d subshells) + the lanthanide series &
actinide series (have valence electrons in s & f subshells)
● In the modern IUPAC identification system: groups are numbered 1-18
(2.2) TYPES OF ELEMENTS
● 3 groups of elements with similar characteristics:
1. Metals
2. Nonmetals
3. Metalloids (A.K.A. semimetals)
(2.2.1) METALS
● Metals → found on left side & middle of PT
○ Include:
■ Active metals
■ Transition metals
■ Lanthanide & actinide series
○ Lustrous (shiny) solids – except mercury (liquid under normal conditions)
○ Generally have high melting points & densities – BUT there are exceptions
○ Have the ability to be deformed without breaking:
■ Malleability: the ability of metal to be hammered into shapes
■ Ductility: the ability of metal to be pulled or drawn into wires
○ At the atomic level → defined by:
■ Low effective nuclear charge
■ Low electronegativity/high electropositivity
■ Large atomic radius
■ Small ionic radius
■ Low ionization energy
CHAPTER 2: THE PERIODIC TABLE
(2.1) THE PERIODIC TABLE
● Periodic Table of the Elements → 1st published by Dmitri Mendeleev (a Russian chemist) in
1869
↳ Showed that ordering the known elements by atomic weight revealed a pattern of
periodically recurring physical & chemical properties
○ Has since been revised to organize elements based on increasing atomic number
instead (with work of English physicist Henry Moseley)
○ Creates a visual representation of the periodic law: “The chemical & physical
properties of the elements are dependent, in a periodic way, upon their atomic
numbers.”
● PT arranges elements into periods (rows) & groups/families (columns) – based on atomic
number
○ There are 7 periods representing the principal quantum numbers: n = 1 → n = 7
■ Each period is filled sequentially
■ Each element in a given period has 1 more proton & 1 more electron than
the element to its left (in their neutral states)
○ Groups → contain elements with the same electron configuration in their valence
shell + share similar chemical properties
● Valence electrons: the electrons in the valence shell
○ Farthest from nucleus & have the greatest amount of potential energy
○ Able to become involved in chemical bonds with valence electrons of other atoms →
largely determine chemical reactivity & properties of the element
● The Roman numeral above each group = the number of valence electrons elements in that
group have in their neutral state
○ NOTE: Roman numerals 1-10:
1. I
2. II
3. III
4. IV
5. V
6. VI
7. VII
8. VIII
, 2
9. IX
10. X
○ Roman numeral is combined with letter A or B to separate the elements into 2
larger classes:
1. A elements A.K.A. representative elements → include groups IA → VIIIA
↳ These elements have their valence electrons in the orbitals of either s
or p subshells
2. B elements A.K.A. nonrepresentative elements → include both the transition
elements (have valence electrons in s & d subshells) + the lanthanide series &
actinide series (have valence electrons in s & f subshells)
● In the modern IUPAC identification system: groups are numbered 1-18
(2.2) TYPES OF ELEMENTS
● 3 groups of elements with similar characteristics:
1. Metals
2. Nonmetals
3. Metalloids (A.K.A. semimetals)
(2.2.1) METALS
● Metals → found on left side & middle of PT
○ Include:
■ Active metals
■ Transition metals
■ Lanthanide & actinide series
○ Lustrous (shiny) solids – except mercury (liquid under normal conditions)
○ Generally have high melting points & densities – BUT there are exceptions
○ Have the ability to be deformed without breaking:
■ Malleability: the ability of metal to be hammered into shapes
■ Ductility: the ability of metal to be pulled or drawn into wires
○ At the atomic level → defined by:
■ Low effective nuclear charge
■ Low electronegativity/high electropositivity
■ Large atomic radius
■ Small ionic radius
■ Low ionization energy
