Which trend is observed as the first four elements in group 17 on the periodic table are considered in order of increasing atomic number

ANSWER:

The melting and boiling points increase in order of increasing atomic number.

The size of the nucleus increases in order of increasing atomic number.

Ionization energy decreases in order of increasing atomic number.

Electronegativity decreases in order of increasing atomic number.

Electron Affinity decreases in order of increasing atomic number.

The reactivities decrease in order of increasing atomic number.

EXPLANATION:

NAME     MELTING POINT    BOILING POINT

Fluorine    -220              -188

Chlorine          -101                       -35

Bromine           -7.2                58.8

Iodine            114                184

Melting and Boiling points increase as shown above.

NAME     COVALENT RADIUS    IONIC RADIUS

Fluorine    71                        133

Chlorine          99                          181

Bromine           114                  196

Iodine            133                 220

Size increases as shown above.

NAME            FIRST IONIZATION ENERGY

Fluorine              1681

Chlorine             1251

Bromine              1140

Iodine               1008

Ionization energy decreases as shown above.

NAME        ELECTRONEGATIVITY

Fluorine     4

Chlorine           3

Bromine           2.8

Iodine            2.5

Electronegativity decreases as shown above.

NAME      ELECTRON AFFINITY

Fluorine    -328.0

Chlorine    -349.0

Bromine    -324.6

Iodine     -295.2

Electron affinity decreases as shown above.

REACTIVITY

The reactivities of the halogens decrease. This is due to the fact that atomic radius increases in proportion with an increase of electronic energy levels. This decreases the pull for valence electrons of other atoms, minimizing reactivity.