Which periodic trend does not agree with observed trends on the periodic table?

ionization energies generally decrease from left to right across a period of
elements

the ionization energies of Group 2 elements are less than that of Group 3
elements

atomic radii increase from top to bottom down a group of elements

as the atomic numbers of the halogens increase, the electronegativities decrease

The two naturally occurring isotopes of chlorine are 35cl (34.969 amu, 75.77%) and 37cl (36.966 amu, 24.23%). the two naturally occurring isotopes of bromine are 79br (78.918 rm amu, 50.69%) and 81br (80.916 amu, 49.31%). chlorine and bromine combine to form bromine monochloride, brcl. 1. how many peaks will be present in a mass spectrum for brcl? the four combinations of molecule possible given these four isotopes are: 81br37cl, 81br35cl, 79br37cl, and 79br35cl. 2. what are the masses of the four different brcl molecules? express the masses using six significant figures, in decreasing numeric order (highest to lowest), separated by commas.

About 3% of the water on earth is freshest. only about 40% of that freshwater is available for human use. why is so much freshwater unavailable for human use?

How many neutrons does an element have if its atomic number is 50 and its mass number is 166