what doe sit mean when the percent error is negative? does it mean that the actual amount needed in the experiment so that it could react was less? and what doe sit have to with limiting and excess reactants.

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☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts