Not always. The reason being,  increasing atomic number doesn't always equate to increasing mass is because many atoms don't have a number of neutrons equal to the number of protons. In other words, several isotopes of an element may exist. If a sizeable portion of an element of lower atomic number exists in the form of heavy isotopes, then the mass of that element may (overall) be heavier than that of the next element. If there were no isotopes and all elements had a number of neutrons equal to the number of protons, then atomic mass would be approximately twice the atomic number (approximately because protons and neutrons don't have exactly the same mass... the mass of electrons is so small that it is negligible). Different periodic tables give differing atomic masses because the percentages of isotopes of an element may be considered changed from one publication to another.

Atoms cannot be divided using chemicals. They do consist of parts, which include protons, neutrons, and electrons, but an atom is a basic chemical building block of matter.

The element symbol for oxygen is O and its atomic number is 8. The mass numbers for oxygen must be 8 + 8 = 16; 8 + 9 = 17; 8 + 10 = 18. respectively

Some of the duties of a chemist could be:

• Analyze, synthesize, purify, modify and characterize chemical or biochemical compounds
• Develop and conduct programs of analysis to ensure quality control of raw materials, chemical intermediates or final products
• Conduct programs of sample and data collection and analysis to identify and quantify environmental toxicants
• Conduct research to develop new chemical formulations and processes and devise new technical applications of industrial chemicals and compounds
• Conduct research to discover, develop and refine, and evaluate new products
• Conduct fundamental and applied research into the synthesis and properties of chemical compounds and the mechanisms of chemical reactions
• Investigate chemical aspects of the mechanisms of drug action, the diagnosis and treatment of disease, organ function and the assessment of health
• Participate in interdisciplinary research and development projects working with chemical engineers, biologists, microbiologists, agronomists, geologists or other professionals
• Act as technical consultant in a particular field of expertise
• May participate in the commercialization of new products
• May supervise other chemists and chemical technicians and technologists.