Answer:
The columns of the table represent groups, or families, of elements. The elements in a group often look and behave similarly, because they have the same number of electrons in their outermost shell
Talking about ions, a cation has a positive charge. That means a positive charge is gained by an atom that gives out electrons.
<span>Kr> Br> As> Se> Ge> Ca> Ga > K </span>
The rate of effusion of H₂ : 7.2 x 10⁻² m/s
<h3>Further explanation </h3>
Graham's law: the rate of effusion of a gas is inversely proportional to the square root of its molar masses or
the effusion rates of two gases = the square root of the inverse of their molar masses:

or

MW₁ O₂ = 32 g/mol
MW₂ H₂ = 2 g/mol
