Unit 1: Atomic Structure and Properties

Comprehensive flashcards covering the concepts from Unit 1 of AP Chemistry, including atomic structure, mass spectrometry, the mole, periodic trends, and electron configurations.

What information is provided by the atomic number in an element's box on the periodic table?

The number of protons in the nucleus of an atom.

In a neutral atom, how is the number of electrons determined?

The number of electrons is equal to the atomic number (the number of protons).

Define average atomic mass as shown on the periodic table.

The weighted-average mass of a single atom in atomic mass units (amu), which numerically equals the mass of 1 mole of atoms in grams per mole ($g/mol$).

What are the common names for Group 1, Group 2, and Group 17 on the periodic table?

Group 1: Alkali metals; Group 2: Alkaline earth metals; Group 17: Halogens.

What characterizes the members of Group 18?

Noble gases.

What is the relationship between mass number and subatomic particles?

$Mass number = protons + neutrons$.

Define isotopes.

Atoms of the same element (same number of protons) with different numbers of neutrons.

What is the specific value of Avogadro's number for 1 mole of particles?

$6.02214076 \times 10^{23}$ representative particles.

What are the standard temperature and pressure (STP) values mentioned in the lecture?

$1\,atm$ and $273\,K$.

According to the ideal gas law at STP, what volume does 1 mole of an ideal gas occupy?

$22.4\,L$.

How does a mass spectrometer separate atoms?

Atoms are ionized (often to $+1$), accelerated, and separated by their mass-to-charge ratio.

In a mass spectrum, what do peak position and peak height/area indicate?

Peak position corresponds to isotopic mass; peak height or area corresponds to relative abundance.

What is the formula for calculating average atomic mass from isotopes?

$average\,atomic\,mass = f_1m_1 + f_2m_2 + \dots$, where $f$ represents fractional abundance and $m$ represents isotopic mass.

How is the mass percent of an element in a compound calculated?

$\frac{\text{Total mass contributed by the element}}{\text{Molar mass of the compound}} \times 100\%$.

Differentiate between a homogeneous and a heterogeneous mixture.

Homogeneous mixtures are uniform throughout (e.g., air), while heterogeneous mixtures are nonuniform (e.g., sand in water).

What conversion factor relates mass percent to parts per million (ppm)?

$1\% = 10,000\,ppm$.

Define molarity ($M$).

$M = \frac{\text{moles solute}}{\text{liters solution}}$.

What is the difference between an empirical formula and a molecular formula?

An empirical formula is the simplest whole-number ratio of elements; a molecular formula represents the actual number of atoms of each element in a molecule.

What is the Aufbau principle?

Electrons fill lower-energy orbitals before filling higher-energy ones.

What does Hund's rule state?

In equal-energy orbitals, electrons spread out singly before pairing.

State the capacity of the s, p, d, and f sublevels.

s: 2; p: 6; d: 10; f: 14.

From which orbitals are electrons removed first when transition metals form cations?

The highest principal energy level (outer s electrons) is removed first, even if a d sublevel was filled later.

What does peak height represent in Photoelectron Spectroscopy (PES)?

The number of electrons in a specific subshell.

What is the qualitative relationship of Coulomb's Law for atomic attraction?

More charge (protons) increases attraction, while greater distance (radius) decreases attraction ($F = k \frac{q_1q_2}{r^2}$).

Define effective nuclear charge ($Z_{eff}$).

The net positive charge felt by an electron after accounting for shielding by inner electrons.

How does atomic radius change moving across a period from left to right?

It decreases because $Z_{eff}$ increases, pulling electrons closer in the same energy level.

How does atomic radius change moving down a group?

It increases because electrons occupy higher energy levels and shielding increases.

How does the size of an anion compare to its neutral atom?

Anions are larger due to increased electron-electron repulsion within the same shell.

What is the general trend for first ionization energy across a period?

It generally increases as $Z_{eff}$ increases and atoms become smaller.

Why is the second ionization energy always greater than the first?

The remaining electrons experience a higher effective attraction and a stronger proton-to-electron ratio after the first electron is removed.

Which element has the highest electronegativity?

Fluorine.

How are the numbers of valence electrons for main-group elements typically determined?

By the group number (e.g., Group 1 has 1; Group 17 has 7).

What are the common ion charge exceptions for Zinc and Silver?

Zinc typically forms $+2$ and Silver typically forms $+1$.