1. Suppose you had come along before Mendeleev and were tasked with

organizing the elements into a pattern others could understand. Describe your

arrangement and how you would determine where elements would be placed.

Can you think of any problems your design might create?

2. The first periodic table was organized according to atomic mass, but the

current periodic table is arranged according to atomic number. What is the

difference between atomic mass and atomic number, and why is the atomic

number now the basis for the periodic table?

3. How would the periodic table look differently if it was arranged according to

atomic mass? Focus on Periods 1-4 to complete your answer.

1. There would be two different tables, one arranged by mass and the second arranged by the chemical reactions the elements are known for

2. a. The difference is that the atomic mass is fixed and is 2 or more times the atomic number which is variable

b. The atomic number is the bases of the periodic table because it reflects the unique identity as well as the chemical and physical properties of the atoms more than the atomic number

3. The table formed by the atomic mass is not representative of the chemical properties of the elements

Explanation:

1. The elements would have been arranged by mass and by order of reaction such that there would be two tables where the first table will list all the known elements arranged by mass and the second table will group the elements in the order in which they can react or the kinds of compounds they can form such as oxides, nitrides etc

2. a. The atomic number, Z, is determined by the definitive number of protons contained in the nucleus of an atom and it is used for the classification of an atom as a particular element based on the its equivalent atomic number

The atomic number defines the chemical behavior of an an element because it is equal to the number of electrons present in a neutral atom

The atomic mass or mass number, A, is the total of the mass of the protons and the neutrons present in an atom

The neutron is electrically neutral, allowing its quantity to vary without significantly impacting on the chemical behavior of the atom, hence two different elements can have the same number of neutrons

Therefore, the difference is that the atomic mass is fixed and is 2 or more times the atomic number which is variable

b. The atomic number is the bases of the periodic table because it reflects the unique identity as well as the chemical and physical properties of the atoms more than the atomic number

3. If the periodic table was arranged according to the atomic mass, we would have;

Groups

H

He Li B C O F Na

Be N Ne Mg S Ar Sc

O Si Ca Ti Zn Se

It is seen that the above table is not representative of the chemical properties of the elements.