Chemistry Practice Test: Periodic Trends

Across period 2 the nuclear charge grows while the outer electrons stay in the same energy level, so atoms get smaller from left to right. Fluorine is the smallest and nitrogen the largest of the three.

Na loses its single 3s electron, leaving the ion with electrons only in levels 1 and 2, much closer to the nucleus. The number of protons does not change when an ion forms.

With the same 10 electrons, the ion with the fewest protons holds them least tightly. Oxygen has only 8 protons, so O²⁻ is the largest, while Mg²⁺ with 12 protons is the smallest.

Ionization energy generally rises across a period as nuclear charge increases, and the noble gas at the end has the most stable electron arrangement. Chlorine is high, but argon is higher.

The huge jump comes after the second electron, so the atom has two valence electrons and then a stable inner shell. That pattern fits Group 2 (these are the values for magnesium).

Atoms on the right side have a larger effective nuclear charge and attract bonding electrons more, while atoms lower in a group hold them farther away. That is why fluorine, at the top right, is the most electronegative element.

Metallic character means how easily an atom loses electrons, and it increases down a group and toward the left. Cesium sits near the bottom of Group 1, so it loses its outer electron most easily.

Halogens react by gaining one electron, and the small fluorine atom attracts an extra electron most strongly. Halogen reactivity decreases down the group, so iodine is the least reactive of the four.

Both metals have one valence electron, but potassium's is in the fourth energy level, so it is held less tightly and removed more easily. That gives potassium a lower, not higher, ionization energy.

Dull, brittle and semiconducting is the typical behavior of a metalloid, and silicon is the classic example. Sulfur is also dull and brittle, but it does not conduct electricity.