Which of the following equations is balanced

- Third equation, is balanced.

Explanations:- A balanced equation has equal number of atoms of each element on both sides.

In first equation, both sides have two Al, so Al is balanced. Both sides have three O and so O is also balanced. Left side has three Fe but the right side has only one Fe and so the reaction is not balanced as it has unequal Fe on both sides.

In second equation, Al is balanced as both sides have two Al. Fe and O are not balanced as left side has one Fe and one O where as the right side has three Fe and three O. So, the reaction is not balanced.

In third equation, both sides have two Al, three Fe and three O and it makes the reaction balanced. So, the third equation is balanced.

In fourth equation, both sides have three Fe and three O and so they are balanced but Al is not balanced as the left side has one Al where as the right side has two Al. So, this equation is not balanced.

Hence, the only correct choice is third equation,

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.  

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8