Instructor’s Copy
Lab Worksheet – The Latest Trend
The data on this table depends on the property assigned.
Table 1: Scale data on ________________________________ (which property)
Scale information
Length of soda straw (cm) 19.6
Half the straw length (cm) 9.8
Largest value of property to be
investigated
Scale for straw length vs.
property (cm):1/2 straw length
/largest value of property
Property modeled
Atomic number (#
of protons)
#
Mass
MP
BP
Dens.
Radii
Ion
Elect
88
226
3620
4200
11.9
280
2372
4.0
.003
.002
.82
.035
.004
2.45
.11
.04
Table 2: Trends on the periodic table
Trend down groups
Trend from left to right in period
Increases going down
Increases going right
Atomic mass
Increases going down
Increases going right
Melting point
Except for hydrogen, decreases
going down
Increases for first 4, then a major
drop with continued decrease
Boiling point
Except for hydrogen, decreases
going down
Increases for first 4 then decreases
Density
Except for sodium, increases going
down
Atomic radius
Increases going down
In general, it increases for the first
4, then a major drop with slight
increases.
Decreases going right until it
reaches noble gas, which is bigger
Ionization energy
Decreases going down
Increases going right
Electronegativity
Decreases going down
Increases going right
QUESTIONS:
1. What is the trend in atomic number? Using the idea that the atomic number is the number of
protons, explain why this trend occurs.
The table is set up by increasing # of protons (atomic number).
2. What is atomic mass? Explain why this trend occurs.
Atomic mass is the mass of the protons + neutrons. As the # of protons increases, so does
the number of neutrons and electrons. This increases the mass.
3. What is the trend in melting and boiling points? Explain why this might occur.
Both points decrease going down the groups because the elements
4. What is density? Explain why this trend might occur.
Density is the mass/volume of a substance. It tells how tightly packed the atom is. In
general, the density increases for the first 4 columns in a period because the mass
increases while the volume does not change much. After the first 4, the volume decreases
as the electrons are held slightly closer. Going down the group, the density generally
increases as a large amount of mass is added to the nucleus.
5. What is atomic radii? Explain why this trend might occur.
Half the distance from the center of the nucleus to the outer electrons. Radius increases
going down the group as more energy levels are added to the atom. Radius decreases
going right because the electrons are held closer to the nucleus as the energy level fills up.
6. What is ionization energy? Explain why this trend is present.
Ionization energy is the energy needed to remove the most loosely held electron. This is
directly related to radius, it decreases as the radius increases because the electrons are
easier to pick off.
7. What is electronegativity? Explain why this trend might occur.
A measure of the tendency of an atom to attract a bonding pair of electrons. As the atom
gets bigger, it does not attract its own electrons so it cannot pick electrons off another
atom.
8. What is the relationship between electronegativity and ionization energy?
They are directly related. If the atom can’t hold its electrons to its nucleus, it can’t attract
other electrons either.
9. What is the relationship between atomic number and atomic mass?
Protons have mass. If the number of protons increases, the mass increases.
10. What is the relationship between atomic radius and other properties on the table.
The atomic radius seems to directly affects the ionization energy and the electronegativity
because the larger the atom, the less likely it is to hold its own electrons tightly or attract
electrons from other atoms.