Download Periodic Trends

Name: _____________________________
Block: _____ Date: __________________
Periodic Trends
Many properties of the elements tend to change in a predictable way, known as trends. Trends among
elements in the periodic table include their sizes and their abilities to lose or attract electrons.
Atomic Size
Definition:
Atomic size is related the atomic radius of an element, which is defined as half the distance between
adjacent nuclei of two atoms of that element.
The Trend:
Going across the periodic table, atomic radius tends to get smaller. This
is because there is an increase of positive charge (more protons), also
known as nuclear charge, which has a greater attraction to the
valence electrons (which are increasing as well). This pulls the
valence electrons closer to the nucleus.
Going down the periodic table, atomic radius tends get bigger
within a group. Even though the number of protons is increasing,
new energy levels are added as you move down which move the
valence electrons further away. Also, the additional orbitals
between the nucleus and the outer electrons are occupied, these
electrons shield the out electrons from the nucleus.
1. Summarize in your own words what atomic size is and the trends going across and down the
periodic table. Be sure to explain WHY these trends take place. Use an analogy (like
magnets) if needed.
Ionization Energy
Definition:
The energy required to remove an (one) electron from an atom.
Another way to look at it is how strongly the atom’s nucleus
hold onto its valence electrons. The more valence electrons it
has, the hard it is for the atom to give one up.
The Trend:
For the first ionization energy, going across the periodic table
the ionization energy will generally increase. This is because
the nuclear charge increases, pulling the valance electrons
tighter to the nucleus.
Going down the periodic table the ionization decreases because
the electrons are further from the nucleus and there is more shielding which makes it so less energy is
required to remove an electron.
2. Summarize in your own words what ionization energy is and the trends going across and
down the periodic table. Be sure to explain WHY these trends take place. Use an analogy if
needed.
Electronegativity:
Definition:
Electronegativity is the relative ability of an atom to attract electrons in a chemical bond. This helps
determine if a bond is nonpolar, polar, or ionic. The atom with the higher electronegativity more strongly
attracts the bond’s electrons.
The Trend:
Going across the periodic table electronegativity increases as the nuclear charge increases. Noble gasses
do not have electronegativity values because they do not form chemical compounds.
Going down the periodic table electronegativity decreases because there is more shielding from the
nucleus.
3. Summarize in your own words what is electronegativity and the trends going across and
down the periodic table. Be sure to explain WHY these trends take place. Use an analogy if
needed.
4. On the periodic table below, draw arrows to indicate the general trends for atomic size, ionization
energy, and electronegativity both across and down the periodic table. Be sure to label each arrow
(you should have 6 total).
5. Which element has the largest atomic size?
_________________________________
6. Which element has the highest ionization energy?
_________________________________
7. Which element has the largest electronegativity?
_________________________________
8. Rank the following elements by increasing atomic radius: carbon, aluminum, oxygen, potassium.
9. Rank the following elements by increasing electronegativity: sulfur, oxygen, neon, aluminum.
10. Why does fluorine have a higher ionization energy than iodine?
11. Why do elements in the same family generally have similar properties?
12. What trend in atomic radius occurs down a group on the periodic table? What causes this trend?
13. What trend in ionization energy occurs across a period on the periodic table? What causes this
trend?
14. Circle the atom in each pair that has the largest atomic radius.
a. Al or B
b. Na or Al
c. S or O
d. O or F
e. Br or Cl
f. Mg or Ca
15. Circle the atom in each pair that has the greater ionization energy.
a. Li or Be
b. Ca or Ba
c. Na or K
d. P or Ar
e. Cl or Si
f. Li or K
16. Circle the atom in each pair that has the greater electronegativity.
a. Ca or Ga
b. Br or As
c. Li or O
d. Ba or Sr
e. Cl or S
f. O or S