Answer:
Element is made up of the atoms or isotopes. Isotopes are where only neutrons change in number, such as 3 turning to 2 or to 5. Atom is where it is not changed and it is the original, and example is instead of Carbon13 it is just Carbon. I hope this helps.
An SI base unit for measuring length would be meters.
I believe the correct answer would be that electronegativity generally increases moving from left to right across a period. The periodic table of elements is arranged so that trends of the properties of the elements can be shown. For electronegativity, it decreases from right to left which means for the opposite direction it increases.
I can’t see the whole question......
