The above table shows land features and the boundary type that has formed those features. Choose the best choice to complete the boundary types for both oceanic ridges
and terrestrial mountain ranges.

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.  

the correct answer would be d. hope this !

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.