Why do carpenters use a screw instead of nails to join two pieces of wood?

Screws have phenomenal tensile strength which is far greater than nails. Screws build a tight adhesion between two pieces of wood.  

Nails are used for joints, because even after multiple twists the wood at the joints will remain together when nails are used. But a screw will come off after a single twist, if screws are used to hold wood at the joints.  

For any static wood work screws are better than nails because of their tensile strength.  

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.