Elements in a group (column) on the periodic table can be expected to have similar atomic masses.

atomic numbers.

numbers of neutrons.

properties.

Elements in a group (column) on the periodic table have similar properties.

Element in the periodic table are arranged according to there atomic number.

The atomic number of an element is the proton number of an element.  

Elements in the same group have similar properties. The properties maybe chemical or physical properties.

For example group 1 elements are very reactive. This group 1 elements have charges of +1.  There cations are represented as A⁺¹.

Generally,  elements in the same groups have similar properties.  

These properties maybe there metallic nature, reactivity, Valence electrons, valency, atomic size, ionization energy, electron-positivity and electron-negativity

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The answer is properties

Explanation:

Atomic masses,numbers and numbers of neutrons varies from each element on the periodic table but once they are in the same group they are expected to have similar properties.

i think it is true since you can test the answer and can use observations to complete it.