Chapter U1.13, Problem 1E

Interpretation Introduction

Interpretation:

Differences between atomic number and atomic mass is to be explained.

Concept introduction:

A periodic table was developed by scientists to arrange the elements based on the patterns in their properties. Modern periodic table is a storehouse of information about the elements. An atom is made of particles called electrons, protons and neutrons.

Answer to Problem 1E

Differences between atomic number and atomic mass are:

Atomic number- The number of protons in the nucleus of an element is called atomic number. In a neutral atom, the atomic number is also equal to the number of electrons. It is unique for each element. All isotopes have the same atomic number. This is a whole number. Number of neutrons is not considered. Number of protons is considered in calculation.

Atomic mass - Atomic mass is the average of the masses of the isotopes of an element. It can be similar or different for two isotopes of different elements. Isotopes of an element have different atomic masses. This is often a decimal number. Number of neutrons is considered. Masses and abundance of isotopes are used in calculation.

Explanation of Solution

Given information :Atomic number and atomic masses are two properties of an element.

From the periodic table we get the following information about elements:

Element name, symbol, atomic number and average atomic mass

Each square of the periodic table looks like the one given below:

Atomic number gives the number of protons which is also equal to the number of electrons. It has no units. It is a whole number as the number of protons is used to calculate atomic number of an element. All isotopes of an element will have same atomic number. Number of neutrons is not considered. Atomic number is unique for each element as every element has different number of protons.

Atomic mass is the sum of number of protons and number of neutrons. It is expressed in amu. It is often written in decimal number as it is calculated by taking average of masses of isotopes of an element in a sample. Since each isotope has a different number of neutrons, it is used to calculate atomic masses.

Conclusion

The periodic table gives us information such as element name, symbol, atomic number and average atomic mass. Number of protons is equal to number of electrons and is known as atomic number. Atomic mass is the average of the masses of the isotopes of an element.