Since all atoms have negatively charged electrons, shouldn't every sample of matter have a negative charge? explain.

Answer is: no, every sample does not have a negative charge.

Beside negatively charged electrons, atoms have positively charged protons, so atoms have neutral charge.

Atomic number is the number of protons, which is characteristic of a chemical element. For example, iron (Fe) is an element with atomic number 26, which means it has 26 protons and 26 electrons (in neutral atom, number of protons is equal to number of electrons).

The electron (symbol: e⁻) is a subatomic particle whose electric charge is negative one elementary charge.

Proton is a subatomic particle with a positive electric charge of +1e elementary charge.