1. moving from left to right across a row of the periodic table, which of the following values increases by exactly one from element to element? (1 point) isotope number atomic number atomic mass unit mass number 2. the atomic mass of an element is (1 point) the sum of the protons and neutrons in one atom of the element. twice the number of protons in one atom of the element. a ratio based on the mass of a carbon-12 atom. a weighted average of the masses of an element’s isotopes. 3. which general statement does not apply to metals? (1 point) most metals are ductile. most metals are malleable. most metals are brittle. most metals are good conductors of electric current. 4. group 7a of the periodic table contains the (1 point) most reactive nonmetals. most reactive metals. least reactive nonmetals. least reactive metals. 5. the unit for atomic mass is (1 point) gram. amu. pound. none of the above