posted by liz .
Can someone explain this to me.
Element D has 6 protons and 7 neutrons
Element F has 7 protons and 7 nuetrons
are the pair isotopes or different elements
Do you mean to identify element D and element F. If so, look at the number of protons. That is the atomic number of the element AND it is the number of protons in the nucleus. Therefore, element D has an atomic number of 6 which makes it carbon (look on the periodic chart at atomic number 6 element). (Carbon has isotopes--isotopes are atoms of the same element but the nucleus contains a different number of neutrons.) Thus, 613C has 6 protons and 7 neutrons in the nucleus. I will let you decide element F now that you see how to do it.