chem unit 5

test on nov 19

What are the general properties of metals?

Solid at room temp, malleable, ductile, good conductors.

What are the general properties of nonmetals?

Mostly gases at room temp, brittle, poor conductors.

What are metalloids, and what is their key property?

Elements with properties of metals and nonmetals; they are semiconductors.

What are alkali metals, and where are they found?

Group 1 elements; silvery, soft, reactive with water, not found freely in nature.

What are alkaline earth metals, and how do they differ from alkali metals?

Group 2 elements; harder, denser, and less reactive than alkali metals.

What are halogens, and why are they so reactive?

Group 17 elements; they need 1 electron to complete their outer shell.

What are noble gases, and why are they unreactive?

Group 18 elements; they have full outer electron shells.

What is the octet rule?

Atoms gain, lose, or share electrons to achieve 8 valence electrons.

What are the two ways elements achieve a full octet?

By gaining/losing electrons (ions) or sharing electrons (covalent bonding).

What is effective nuclear charge (Zeff)?

The net positive charge experienced by an electron, calculated as Z - SZ.

How does atomic radius change across a period?

It decreases due to increasing Zeff, pulling electrons closer to the nucleus.

How does atomic radius change down a group?

It increases because electrons are added to higher energy levels.

What is ionization energy?

The energy required to remove an electron from an atom.

How does ionization energy change across a period?

It increases because Zeff strengthens the attraction to outer electrons.

How does ionization energy change down a group?

It decreases because outer electrons are farther from the nucleus and shielded.

What is electronegativity?

An atom’s ability to attract electrons in a chemical bond.

How does electronegativity trend on the periodic table?

It increases across a period and decreases down a group.

What is electron affinity?

The energy change when an atom gains an electron; often releases energy (negative).

How do cations and anions differ in size from their parent atoms?

Cations are smaller; anions are larger.

Which element has the highest electronegativity?

Fluorine, with a value of 4.0.

What element has the lowest electronegativity?

Francium, with a value of 0.7.

How does electron affinity change across a period and down a group?

Electron affinity generally becomes more negative (or releases more energy) across a period as the nuclear charge increases, while it becomes less negative (or requires less energy release) down a group due to increased atomic size and electron shielding.

What factors influence electronegativity trends in the periodic table?

Electronegativity increases across a period due to increased nuclear charge with the same shielding effect, and decreases down a group due to increased atomic size and electron shielding.

What are the trends in ionization energy down a group?

Ionization energy decreases down a group because outer electrons are farther from the nucleus and experience greater shielding, making them easier to remove.

What are the trends in atomic radii across periods and down groups on the periodic table?

Atomic radii decrease across a period due to increasing effective nuclear charge, pulling electrons closer to the nucleus, and increase down a group as additional electron shells are added, increasing the distance from the nucleus.