Question

. As the elements in Period 3 are considered in order of increasing atomic number, there is a general decrease in

atomic mass
atomic radius
electronegativity
first ionization energy

Answer 1

Atomic radius, because the number of electrons and protons increases by 1 each time you move right along period so there is greater electrostatic attraction (electrons are pulled to the nucleus more strongly) and there is no additional shielding to counteract this since the number of inner energy levels does not increase along a period.