Atoms & Electrons (College Board AP® Chemistry): Flashcards

In Coulomb's Law, F = kq₁q₂/r², the symbol r represents the distance between the two charges, measured in meters.

F = k(q₁q₂)/r²

F = (8.99 × 10⁹) × (1.602 × 10^-19) × (−1.602 × 10^-19) ÷ (1 × 10^-10)²

F = −2.31 × 10^-8 N

The negative sign indicates an attractive force, as the charges are opposite.

False.

A negative Coulombic force indicates an attractive interaction. This occurs when the two charges are opposite in sign (one positive, one negative), such as a proton and an electron.

Coulomb's Law states that the electrostatic force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.

Valence electrons are the electrons in the outermost shell of an atom. The number of valence electrons equals the principal group number in the periodic table and determines the chemical properties of the element.

The energy of a photon (E) is directly proportional to its frequency (v), given by E = hv, where h is Planck's constant (approximately 6.626 × 10^-34 J·s). Higher frequency photons carry more energy.

False.

When an electron absorbs a photon, it gains energy and jumps from an inner shell to an outer shell (higher energy level). When a photon is emitted, the electron falls from an outer shell to an inner shell.

The p subshell contains three dumbbell-shaped orbitals, and each orbital can hold a maximum of two electrons.

This gives the p subshell a total capacity of six electrons.

The third shell can hold a maximum of 18 electrons. It contains the 3s (1 orbital, 2 electrons), 3p (3 orbitals, 6 electrons) and 3d (5 orbitals, 10 electrons) subshells.

True.

The farther a shell is from the nucleus, the higher the energy of the electrons within it. This is why electrons fill inner shells first before occupying outer shells.

Electrons in the inner shells of an atom are called core electrons, while electrons in the outermost shell are called valence electrons.

The Aufbau Principle states that electrons fill the lowest energy orbitals first before occupying higher energy orbitals. The order of filling is determined by the Aufbau diagram.

The full electron configuration of fluorine (atomic number 9) is 1s² 2s² 2p⁵.

Step 1: fill 1s with 2 electrons. Step 2: fill 2s with 2 electrons. Step 3: place the remaining 5 electrons in 2p.

True.

Each orbital holds a maximum of two electrons, and they must have opposite spins (one spin-up ↑ and one spin-down ↓). This reflects the Pauli exclusion principle applied to orbital diagrams.

A condensed electron configuration uses the symbol of the closest preceding noble gas in square brackets, followed by the remaining electron configuration. For example, fluorine (1s² 2s² 2p⁵) is written as [He] 2s² 2p⁵, where [He] represents the 1s² core.

Elements in the same group (column) of the periodic table have similar valence electron configurations, which explains why they show similar chemical properties.

True.

The Aufbau diagram shows that 4s has lower energy than 3d and is therefore filled first. This is why the electron configuration of calcium is [Ar] 4s² rather than [Ar] 3d².

Electrons occupy each orbital of equal energy singly (spin-up ↑) before any orbital is doubly occupied, then pair up with an opposite spin (↓) once each equal-energy orbital has one electron. This reflects Hund's rule as shown in orbital diagrams.

Ionization energy is the energy required to remove an electron from an atom or ion in the gaseous state. It is always positive because energy must be supplied to overcome the Coulombic attraction between the electron and the nucleus.

Core electrons repel valence electrons and partially cancel the attractive pull of the nucleus. This reduces the effective nuclear charge experienced by valence electrons, weakening the Coulombic attraction and making it easier (requiring less energy) to remove them.

True.

Although chlorine has more protons, fluorine's valence electrons are in the 2p subshell — much closer to the nucleus than chlorine's 3p electrons. The shorter distance and greater effective nuclear charge in fluorine result in a stronger Coulombic attraction and higher ionization energy.

The ionization energy of an atom increases as the distance of the valence electron from the nucleus decreases and as the effective nuclear charge increases.

Both effects strengthen the Coulombic attraction, making it harder to remove the electron.

Coulomb's Law (F = kq₁q₂/r²) shows that the force holding an electron to the nucleus depends on the effective nuclear charge and the distance. The atom with a greater effective nuclear charge and/or shorter electron-nucleus distance has a stronger attractive force and therefore higher ionization energy.

False.

When comparing atoms across periods, the distance from the nucleus and the shielding effect have more impact than nuclear charge alone. For example, chlorine has a greater nuclear charge than fluorine but a lower ionization energy because its valence electrons are farther from the nucleus and more shielded.

Ionization energy is always positive because removing an electron from a gaseous atom always requires energy.

The electron must overcome the Coulombic attraction to the positively charged nucleus, so energy must be supplied.

Photoelectron spectroscopy (PES) is an experimental technique used to measure the relative energies of electrons ejected from an atom by a source of radiation. The resulting PES spectrum directly reflects the atom's electron configuration.

The x-axis represents binding energy (the energy required to remove an electron from a particular subshell) and the y-axis represents the relative number of electrons removed at each binding energy. Each peak corresponds to a distinct subshell.

True.

The relative height (intensity) of each peak is proportional to the number of electrons in that subshell for the specific element being measured. A subshell containing more electrons produces a taller peak than one with fewer electrons.

In a PES spectrum, electrons in subshells closer to the nucleus have higher binding energy.

Equal peak heights indicate the same number of electrons in each subshell. Three peaks correspond to the 1s, 2s and 2p subshells, each with 2 electrons.

Electron configuration: 1s² 2s² 2p²

False.

Low binding energy indicates electrons in subshells farther from the nucleus, where the Coulombic attraction is weaker and less energy is needed for removal. Electrons close to the nucleus appear at high binding energy.

The number of peaks in a PES spectrum corresponds to the number of distinct subshells occupied in the atom, and the relative height of each peak is proportional to the number of electrons in that subshell.

Three peaks of equal height indicate three subshells each containing the same number of electrons. The subshells are 1s, 2s and 2p, each with 2 electrons — 6 electrons in total.

The element is carbon (C).