The Periodic Table
Chapter 6
I.
Organizing the Elements
Chemist used properties of elements to sort them into groups. One of the first
periodic tables organized the elements in increasing order of atomic mass.
A. Periodic Law- Elements with similar chemical properties appear at
regular intervals when listed in order of increasing atomic number. In
the periodic table elements are arranged in order of increasing atomic
number.
B. Metals, Nonmetals, and Metalloids
1. Metals are located to the left of the stair step line. Metals are shiny,
conduct heat and energy
a) Metals are ductile – can be drawn into a wire.
b) Metals are malleable – they can be hammered into shape.
c) Metals have high densities.
d) Metals have high melting points.
2. Nonmetals right of the stair step line.
a) Nonmetals are poor conductors of heat and energy
b) Nonmetals have low density many nonmetals are gases at room
temperature.
c) Nonmetals have low melting points compared to metals.
3. Metalloids, also called semimetals, have properties of both metals and
nonmetals. B, Si, Ge, As, Sb, Te, At are all semimetals.
II. Classifying the elements
The periodic table displays the symbols of the elements along with information
about the structure of their atoms.
A. Group Names on the Periodic Table. Columns on the periodic table are
called groups and families
1. Alkali metals – group IA except hydrogen (see page 162-163 text
book)
2. Alkaline Earth metals – group IIA
3. Chalcogens – group VIA
4. Halogens – group VIIA. These are the most reactive
5. Noble Gases – group VIIIA These are the least reactive
B. Representative elements – all the columns with an “A.” They are called the
representative elements because they display a wide range of physical and
chemical properties.
C. Transition metals – all the middle area
D. Elements can be sorted into noble gases, representative elements, transition
metals, or inner transition metals based on their electron configuration. (See
chart p.166)
III. Periodic Trends
A. Atomic Radius within a group increases as the atomic number increases.
Group on the periodic table is a column. Period on the periodic table is a row.
Atomic radius within a period decreases as the atomic number increases. As you
go across the table the size decreases.
B. Ions are atoms that have either a negative or positive charge. This happens
when an atoms gains or loses electrons. When an atom loses an electron the ion is
said to have a positive charge and is called a cation. When an atom gains an
electron it is said to have a negative charge and is called an anion.
1. Cations are smaller than the atoms since they have fewer electrons.
2. Anions are larger the atoms since they have more electrons.
C. Ionization energy is the amount of energy required to remove an electron
from an atom.
1. Ionization energy (IE) decreases as you go down the periodic table,
this is because as you get electron further away from the nucleus its
attraction to the nucleus decreases, so the electron can be removed easier.
Ionization increases as you go to the left from the right.
2. He has the highest I E
3. Fr has the smallest I E
D. Electron affinity – amount of energy given off when atom gains an electron.
1. When atom has an extra electron it is called an anion.
Cl + e-  Cl- + energy
2. Electron affinity increases as you go up and to the right.
3. Cl has the highest electron affinity
E. Electronegativity
1. The ability of an atom of an element to attract electrons to itself.
2. Defined as the difference between ionization energy (IE) and electron
affinity (EA)
IE–EA
2
3. Increases as you go up and to the right.
4. F is the most electronegative.
F. When ions have the same number of electrons they are said to be isoelectric
(isomers).
Example:
F- and Na+. In this case both ions would have 10 electrons.
G. Diatomic Elements. Some elements exist as a compound in nature. These are
elements that are bounded to an element of same type. They are H2, N2, O2, F2,
Cl2, Br2, I2. There are a total of 7.
Questions
1. Identify each element as a metal, metalloid, or nonmetal.
a. gold ___metal__
b. silicon __metalloid____
c. sulfur __nonmetal___
d. barium __metal___
2. Identify each property below as more characteristic of a metal or a nonmetal.
a. a gas at room temperature ___nonmetal__
b. brittle ___nonmetal___
c. malleable ___metal___
d. poor conductor of electric current ____nonmetal___
e. shiny ___metal___
3. Where are the alkali metals, the alkaline earth metals, the halogens, and the noble
gases located in the periodic table?
Alkali metals column 1
Alkaline Earth metals column 2
Halogens column 17 also numbered 7A
Noble gases column 18 also numbered 8A
4. Which element in each pair has atoms with a larger atomic radius? (circle the correct
element)
a. sodium
or
lithium
b. strontium or
magnesium
c. carbon
or
germanium
d. selenium or
oxygen
5. Which element in each pair has a higher electronegativity value?
a. Cl
or
F
b. C
or
N
c. Mg
or
Ne
d. As
or
Ca
6. When do ions form? ___When an atom gains or losses electrons.__