Short note of modern periodic table

Hi

In the modern periodic table, the elements are arranged in the order of their increasing atomic number. In the modern periodic table, there are seven horizontal rows called periods and eighteen vertical columns (1 to 18) called groups. The arrangement of the periods and groups results in formation of boxes.

Explanation:

If it's help pls give me Brainliest!!

i'm assuming that the correct answer is indeed the first one/ "a"..

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.