(AKS 3g) Sodium catches on fire when it reacts with water. Which electron configuration represents an element that reacts in a similar way? (DOK 2)
0 152 282 2p 3s 3p6451
O 152 282 2p6352 3p6452
1s22s22p63s23p5
O 152 252 2p 3s23p6

b is the correct

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.