( You ( ( ( are ( correct ( when ( you ( say ( ( the electronegativity ) ( of ( the ( atoms decrease ) ) ) ) ) ) ) ) ) ( as ( you ( ( go down ) ( the ( periodic table ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP You)) (VP (VBP are) (ADJP (JJ correct) (SBAR (WHADVP (WRB when)) (S (NP (PRP you)) (VP (VBP say) (NP (NP (DT the) (NN electronegativity)) (PP (IN of) (NP (DT the) (NNS atoms) (NN decrease)))))))) (SBAR (IN as) (S (NP (PRP you)) (VP (VBP go) (PRT (RP down)) (NP (DT the) (JJ periodic) (NN table)))))) (. .)))
You are correct when you say the electronegativity of the atoms decrease as you go down the periodic table.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (PRP we)) (VP (VBP move) (PRT (RP down)) (NP (NP (DT a) (NN group)) (PP (IN of) (NP (NNS elements)))) (PP (IN on) (NP (NP (DT the) (JJ periodic) (NN table)) (, ,) (NP (PRP$ their) (NN electronegativity))))))) (NP (PRP it)) (VP (VBZ decreases)) (. .)))