Periodic Trends Lab

Introduction: As you know, the periodic table is arranged in order of atomic number (the number of protons), and also by molar/atomic mass of the elements (with some exceptions). Today we will be investigating other trends on the periodic table. There are three trends that you will be noticing today:

1.  Electronegativity – the attraction of an element to outside electrons. The goal is to satisfy the octet rule.

2.  Ionization Energy – the energy required for an element to LOSE a valence electron. Again, the goal is to satisfy the octet rule. The less willing an element is to lose an electron, the ionization energy is higher.

3.  Atomic Radius – the size of the atom from nucleus to end of electron cloud. The radius is affected by the number of protons AND the number of electrons.

For looking at the trends there are a few THINGS TO CONSIDER:

·  Octet Rule – elements desire 8 valence electrons, and will either bond with other compounds, or lose/gain electrons in order to do this (whatever is easier). If an element has 8 valence electrons, they remain the same.

·  Law of Attraction #1 – opposite charges attract. Remember that, for the atom, this is referring to the protons (+) in the nucleus and the electrons (-) in the electron cloud. The more protons the more attraction there will be.

·  Law of Attraction #2 – like charges repel. Remember that, for the atom, this is referring to the electrons (-) in the electron cloud. The more rows of electrons, the more repulsion there will be.

Purpose: To uncover the trends on the periodic table for things like atomic number and mass, as well as introducing other trends such as electronegativity, ionization energy and atomic radius.

Pre-Laboratory Questions:

For the following boxes, which represent the elements being observed in today’s lab, please indicate five things:

·  Element SYMBOL

·  TOTAL PROTONS

·  TOTAL ELECTRONS

·  ROWS of ELECTRONS

·  VALENCE ELECTRONS

sym:
P+:
e-:
rows:
val. e-:
sym:
P+:
e-:
rows:
val. e-:
sym:
P+:
e-:
rows:
val. e-:
sym:
P+:
e-:
rows:
val. e-:

Data and Observations:

In a group of 3, arrange your element cards in the same way that the pre-laboratory question is in. This is a reflection of how the Periodic table actually looks. When you have this arrangement, have 1 member look at electronegativity trends, another look at ionization energy trends, and the third look at atomic radius trends. Record your findings below:

Element with LARGEST / Element with SMALLEST / Any Elements n/a?
(If yes, which?) / General Trend
(what CORNER of the table is HIGHEST?)
Electronegativity
(person #1)
Ionization Energy
(person#2)
Atomic Radius
(person #3)

Post-Laboratory Questions:

Now that you have the data collected, it is time to see WHY these trends exist. For this you need your DATA, and the information in the INTRODUCTION (hint: use the THINGS TO CONSIDER portion)

1.  Looking at the general trend for ELECTRONEGATIVITY:

  1. Why do you think this trend existed across the row?
  1. Why do you think this trend existed down the row?
  1. There was a group of elements that had NO electronegativity. Explain why, for this group, it makes sense.

2.  Looking at the general trend for IONIZATION ENERGY:

  1. Why do you think this trend existed across the row?
  1. Why do you think this trend existed down the row?

3.  Looking at the general trend of ATOMIC RADIUS:

  1. Why do you think this trend existed across the row?
  1. Why do you think this trend existed down the row?