What is a msds?
a document that identifies chemical hazards associated with compounds.
part of a biosafety manual. identifies all chemical reactions.
outlines calibration standards.

A. A document that identifies chemical hazards associated with compounds.

Explanation:

MSDS is an abbreviation that means Material Safety Data Sheet and is a document that describes different characteristics of the products such as chemical properties, chemical compounds, toxicity, health effects, between others; all of these in order to an appropriate human use, and reduce the risk during their manipulation.

Depends on the class of chemical compounds that the product has, the MSDS indicates the labor and environmental cautions.

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explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.