Atomic Radius: This refers to the size of an atom. As you move across a period from left to right, atomic radius generally decreases due to increased nuclear charge pulling electrons closer.
Ionization Energy: This is the energy required to remove an electron from a gaseous atom or ion. It generally increases across a period because increasing nuclear charge makes it harder for electrons to escape.
Electronegativity: This measures how strongly atoms attract bonding electrons. It also generally increases across a period because atoms with more protons can attract electrons more strongly.