How do you think a magnifying glass makes objects appear upside down ?

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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.

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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.  

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.

the answer is a for sure mark brainliest i had got this right on usatestprep