OAT Chemistry Periodic Properties

What determines the order of elements on the periodic table?

Atomic number, which is the number of protons

What does a period tell you?

A period is a horizontal row. Its number generally tells you the highest occupied principal energy level \(n\). Example: Na and Cl are in Period 3 and both have outer electrons in n=3

What do elements in the same group usually have in common?

A group is a vertical column. Elements in the same group generally have similar valence electron configurations, so they often behave similarly.

What’s the difference between the principal and azimuthal quantum numbers?

Principal \(n\) tells you the shell (1, 2, 3…). Azimuthal \(\ell\) tells you the subshell type (\(s,p,d,f\)

What are shielding and effective nuclear charge?

Shielding is when inner electrons weaken the nucleus’s pull on outer electrons. Effective nuclear charge is the net positive charge an electron feels after shielding.

Which direction does atomic radius increase?

Down and left. Down a group, atoms gain electron shells. Across a period to the right, the nucleus pulls electrons in more tightly.

What is first ionization energy, and which way does it increase?

The energy needed to remove one electron from a neutral gaseous atom. It generally increases up and right.

What does a big jump in successive ionization energies tell you?

You’ve removed all the valence electrons and are starting to remove core electrons. A big jump after the second electron means the atom had two valence electrons.

What are two common exceptions to the first ionization energy trend?

Be > B and N > O. Boron loses a higher-energy \(p\) electron. Oxygen loses a paired \(p\) electron, which relieves repulsion.

What is electronegativity, and which way does it increase?

How strongly an atom pulls on shared electrons in a bond. It generally increases up and right. Fluorine is highest

What is electron affinity?

The energy change when a gaseous atom gains an electron. Remember: affinity = add, ionization = remove, electronegativity = pull in a bond

How do you rank a cation, neutral atom, and anion of the same element by size?

Cation < neutral atom < anion. Losing electrons generally shrinks the electron cloud; gaining electrons increases repulsion and expands it.

How do you count the electrons in an ion?

Start with the atomic number. Subtract electrons for a positive charge; add electrons for a negative charge.

How do you rank isoelectronic ions by size?

Isoelectronic means they have the same number of electrons. The species with more protons is smaller.

How do you rank Sr, P, Mg, Mg2+ from smallest to largest

Mg2+ < P < Mg < Sr. Mg2+ lost its outer shell; P is to the right of Mg; Sr is below Mg.

What charges do Groups 1, 2, 16, and 17 commonly form as simple ions?

Group 1 (IA): +1. Group 2 (IIA): +2. Group 16 (VIA): −2 for ions such as oxide and sulfide. Group 17 (VIIA): −1.

Why are noble gases usually unreactive?

They already have a full valence shell. Your book calls them Group 0; they’re also called Group 18.

What’s the difference between Group IVA and Group IVB?

IVA is the carbon family, with ns²np². IVB is the titanium family, with the typical pattern ns²(n-1)d² The A vs. B changes which family the question means.

Where are metals, nonmetals, and metalloids?

Metals: left and center. Nonmetals: upper right, plus hydrogen. Metalloids: along the staircase, such as B, Si, and Ge.

What are the main properties of metals, nonmetals, and metalloids?

Metals conduct well and can usually be shaped or drawn into wires. Nonmetals usually conduct poorly and are often brittle when solid. Metalloids have a mix of properties; silicon is a semiconductor.

Why are many transition metal compounds colored?

Electrons absorb certain wavelengths of visible light to move between split \(d\) energy levels. The light that isn’t absorbed gives the compound its observed color.

What does the Roman numeral in iron(III) mean?

It gives the charge on the metal ion. Iron(III) is Fe³+; iron(ll) is Fe²+

What’s the difference between -ide, -ite, and -ate?

A single-atom anion usually ends in -ide, like chloride (Cl-). Within the same oxyanion family, -ate has more oxygen than -ite: nitrate is NO3-, and nitrite is NO2-

How do you rank hypo-…-ite, …-ite, …-ate, and per-…-ate by oxygen count?

From least to most oxygen: hypo-…-ite → …-ite → …-ate → per-…-ate. Example: hypochlorite ClO- → chlorite ClO2- → chlorate ClO3- → perchlorate ClO4-