Periodic Trends
Finalizing our Understanding of the Organization of the Periodic table
Directions: Read the following paragraph to identify the definitions of the 3 main trends seen within the periodic table.
Once you come across a definition, underline it! Once you have competed the reading, continue to answer the questions
below.
Reading for Information: Periodic Trends
Even though it’s difficult to define the "size" of an atom, since it is too small to hold, atoms do behave in many ways as
though they have characteristic sizes. The atomic radius (AR) of an atom, which is the size of the atom, ranges from
element to element. A million carbon atoms placed side by side would be less than 0.2 millimeters long! Ionization
energy (IE) is the energy needed to remove an electron from an atom. In other words, it is a measure of how much
energy is required to remove a valence electron, and thus a measure of how tightly the atom is holding the electron. The
electron configurations of the elements in group 18 are very stable because they have a full valence layer of electrons.
They have a very high IE and it is extremely difficult to break an electron away, and therefore these elements with 8
valence electrons do not react with other atoms, because they do not need electrons. On the other hand, elements
more willing to give up electrons to become happy have low ionization energies; it takes less work to remove those
electrons from such a giving element. Electronegativity (EN) is the relative attraction of electrons in a bond. In HCl, the Cl
is more electronegative than the H and attracts the electrons. The electrons spend more time around the Cl than the H
because Cl has more attraction for electrons (higher electronegativity). In other words, electronegativity is the ability of
an atom to attract electrons.
1. What is the definition of Atomic Radius?
2. What is the definition of Ionization Energy?
3. What is the definition of Electronegativity?
4. What elements have the greatest Ionization Energy?
5. What groups of elements do you think will have the lowest Ionization Energies?
Directions: Using Graphs to Visualize Trends on the Periodic Table
On the next page you will find 6 different tables. On a separate piece of paper, create a graph for each table, graphing
atomic number versus the trend of interest. Be sure to title your graphs, and label the x-axis and y-axis. Once finished
check graphs with Ms. Herndon before moving on to the questions below
Periodic Trends
Finalizing our Understanding of the Organization of the Periodic table
Electronegativity Across a Period (Row)
Electronegativity Down a Group (Column)
Element
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Atomic Number Electronegativity
3
1.0
4
1.5
5
2.0
6
2.5
7
3.0
8
3.5
9
4.0
Element
Beryllium
Magnesium
Calcium
Strontium
Barium
Radium
Atomic
Number
4
12
20
38
56
88
Electronegativity
1.5
1.2
1.0
1.0
0.9
0.9
Atomic Radius Across a Period (Row)
Element
Atomic Number
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
3
4
5
6
7
8
9
10
Atomic Radius
(10-10 m)
2.1
1.4
1.2
0.91
0.75
0.65
0.57
0.51
Ionization Energy Across a Period (Row)
Atomic Radius Down a Group (Column)
Element
Beryllium
Magnesium
Calcium
Strontium
Barium
Atomic
Number
4
12
20
38
56
Atomic Radius
(10-10 m)
1.4
1.7
2.2
2.5
2.8
Ionization Energy Down a Group (Column)
Element
Atomic Number Ionization Energy
Element
Atomic
(J/mol)
Number
Lithium
3
519
Beryllium
4
Beryllium
4
900
Magnesium
12
Boron
5
799
Calcium
20
Carbon
6
1088
Strontium
38
Nitrogen
7
1401
Barium
56
Oxygen
8
1036
Radium
88
Fluorine
9
1682
Neon
10
2076
Using your graphs you just drew for the above data tables, answer the following questions.
1)
Does electronegativity increase or decrease left to right across a period?
2)
Does electronegativity increase or decrease down a group?
3)
Does ionization energy increase or decrease left to right across a period?
4)
Does ionization energy increase or decrease down a group?
5)
Does atomic radius increase of decrease left to right across a period?
6)
Does atomic radius increase or decrease down a group?
Ionization
Energy (J/mol)
900
736
590
548
502
510