jmol software package provides Molecular Viewer, you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install jmol
jmol is installed in your system.
Make ensure the jmol package were installed using the commands given below,
$ sudo dpkg-query -l | grep jmol *
You will get with jmol package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | Science |
| Package | jmol |
| Version | 12.2.32+dfsg2-1 |
| Description | Molecular Viewer |
| Sub Section | Science |