14 !
i need someone to explain to me how to classify elements on the periodic table. what do all of the letters and numbers on the squares mean. what is atomic numbers, protons, nuetrons, etc. i really don't understand. !

The atomic number is the total amount of protons which are positively charged and the atomic mass is the total number of protons and neutrons (neutron are neutral, they have no charge). Protons and neutrons are in the middle of the element while electrons (negatively charged) are on the outside. The electrons on the outer most shell of the element are called valence electrons. The group number an element has will tell you how many valence electrons they have,but it's tricking because group 16 really has 6 ( so be careful with that). I hoped that helped a little!

It depends on the surface of the levels. the rougher the surface, the greater is the frictional force. for rougher surfaces, you would need to exert greater force to move the object. the concept is that, you must overcome the frictional force in order to bring the object into motion. this is the reason why we add lubricants to the joints so they could easily move. this answer was on