What electrostatic forces hold ionic compounds together in a crystal lattice?

Nondirectional electrostatic attractions between positively charged cations and negatively charged anions.

Give two examples of stable molecules that represent exceptions to the octet rule (one incomplete, one expanded).

Incomplete octet: Boron trifluoride (BF3, 6 valence electrons around B); Expanded octet: Sulfur hexafluoride (SF6, 12 valence electrons around S).

What are resonance structures, and what is the true electronic state of a molecule displaying resonance?

Two or more valid Lewis structures representing delocalized electrons in the same atomic framework; the actual molecule is a weighted quantum mechanical resonance hybrid of all contributing forms.

Why is the first ionization energy of boron slightly lower than that of beryllium, despite boron having a higher nuclear charge?

Boron loses an electron from the higher-energy, more shielded 2p orbital, whereas beryllium loses an electron from a fully filled, stable 2s orbital.

What is electronegativity, and which chemical element has the highest electronegativity on the Pauling scale?

The relative ability of a bonded atom to attract shared electrons in a chemical bond; fluorine is highest with a Pauling value of 3.98.

What is the difference between an element's atomic number (Z) and its mass number (A)?

Atomic number (Z) is the number of protons and defines the element; mass number (A) is the total number of protons plus neutrons in the nucleus.

What is the 'electron sea model' of metallic bonding, and how does it explain electrical conductivity?

Positive metal cations are arranged in a fixed lattice surrounded by delocalized, mobile valence electrons that freely drift under an applied electric potential.

What are the three fundamental subatomic particles, and what are their respective charges and locations in the atom?

Protons (positive +1, nucleus), neutrons (neutral 0, nucleus), and electrons (negative -1, surrounding electron cloud).

What is the molecular geometry of sulfur tetrafluoride (SF4) with 5 electron domains (4 bonding, 1 lone pair)?

Seesaw (lone pair resides in the equatorial position to minimize 90-degree lone-pair/bonding-pair repulsions).

What is the molecular geometry of xenon tetrafluoride (XeF4) with 6 electron domains (4 bonding, 2 lone pairs)?

Square planar (the two lone pairs occupy trans axial positions 180° apart).

How do core electrons differ from valence electrons in chemical reactivity?

Core electrons occupy inner completed shells and do not participate in bonding; valence electrons occupy the outermost principal energy level and govern chemical bonding.

According to Coulomb's law, what two factors increase the lattice energy of an ionic solid?

Higher ionic charges (proportional to Q1*Q2) and smaller ionic radii (inversely proportional to interionic distance r).

How is formal charge calculated for an atom within a Lewis structure?

Formal Charge = (Valence electrons of free atom) - (Non-bonding valence electrons) - 1/2*(Bonding electrons).

What is first ionization energy, and why does it generally increase from left to right across a period?

The energy required to remove the first valence electron from an isolated gaseous atom; it increases across a period due to greater effective nuclear charge holding electrons tighter.

What is the fundamental principle underlying Valence Shell Electron Pair Repulsion (VSEPR) theory?

Electron pairs (bonding and non-bonding lone pairs) around a central atom repel each other electrostatically and adopt a geometry that maximizes their spatial separation.

What do the four quantum numbers (n, l, ml, ms) describe about an electron in an atom?

n is the principal energy level, l is the orbital angular momentum shape (s, p, d, f), ml is the spatial magnetic orientation, and ms is the electron spin (+1/2 or -1/2).

What are the names and group numbers of Group 1, Group 2, Group 17, and Group 18 elements?

Group 1: Alkali metals; Group 2: Alkaline earth metals; Group 17: Halogens; Group 18: Noble gases.

What orbital overlaps form a sigma (σ) bond versus a pi (π) bond?

Sigma bonds form from head-on (axial) end-to-end overlap of atomic/hybrid orbitals; pi bonds form from side-by-side (lateral) overlap of parallel unhybridized p orbitals.

What is the general periodic trend for atomic radius across a period and down a group?

Atomic radius decreases across a period (left to right) due to increasing effective nuclear charge, and increases down a group due to the addition of principal energy shells.

What are London dispersion forces, and what molecular property determines their strength?

Temporary induced dipole-induced dipole electrostatic attractions present in all molecules; their strength increases with greater molecular weight and electron cloud polarizability.

What are the electron-domain geometry and molecular geometry of ammonia (NH3)?

Electron-domain geometry is tetrahedral (4 domains); molecular geometry is trigonal pyramidal (3 bonding pairs and 1 lone pair).

How many sigma and pi bonds are present in a carbon-carbon triple bond (as in ethyne, C2H2)?

One sigma (σ) bond and two orthogonal pi (π) bonds.

How do electronegativity differences determine whether a chemical bond is nonpolar covalent, polar covalent, or ionic?

Differences ~1.7 yield predominantly ionic bonds.

What defines isotopes of a chemical element?

Atoms with identical atomic numbers (same number of protons) but different mass numbers (different numbers of neutrons).

What is electron affinity, and which group of elements has the most negative (exothermic) electron affinities?

The energy change occurring when an electron is added to a neutral gaseous atom; Group 17 halogens have the most exothermic electron affinities because adding one electron completes an octet.

What does the Aufbau principle dictate regarding electron configurations in the ground state?

Electrons fill lower-energy atomic orbitals before occupying higher-energy orbitals.

Why is the bond angle in water (H2O, ~104.5°) smaller than the ideal tetrahedral angle (109.5°)?

The two non-bonding lone pairs on oxygen exert greater electrostatic repulsion than bonding pairs, compressing the H-O-H bond angle.

What is effective nuclear charge (Zeff), and how does electron shielding influence it across a period?

Zeff is the net positive charge experienced by valence electrons (Zeff = Z - S); core shielding stays roughly constant across a period while nuclear charge increases, pulling valence electrons tighter.

What does the Pauli exclusion principle state concerning electrons in an atom?

No two electrons in the same atom can have the exact same set of four quantum numbers; an orbital can hold a maximum of two electrons with opposite spins.

According to Hund's rule, how do electrons occupy degenerate orbitals of equal energy?

Electrons singly occupy each degenerate orbital with parallel spins before any orbital is doubly occupied.

What orbital hybridizations correspond to linear, trigonal planar, and tetrahedral electron geometries?

Linear: sp hybridization; Trigonal planar: sp2 hybridization; Tetrahedral: sp3 hybridization.

What specific structural criteria are required for intermolecular hydrogen bonding to occur?

A hydrogen atom covalently bonded to a highly electronegative, small atom (N, O, or F) interacting with a lone pair on another N, O, or F atom.

Química Orgànica — Bàsic (A1/A2) 3: Atomic Structure, Periodic Table & Bonding

[Català] Química Orgànica: Subatomic particles, electron configurations, periodic trends, ionic and covalent bonding, Lewis structures, and VSEPR geometry

Level: basic
Languages: ca → ca
Cards: 32
Markdown: Química Orgànica — Bàsic (A1/A2) 3: Atomic Structure, Periodic Table & Bonding (.md)

Flashcards (32)

#	Front (Term / Question)	Back (Definition / Answer)
1	What electrostatic forces hold ionic compounds together in a crystal lattice?	Nondirectional electrostatic attractions between positively charged cations and negatively charged anions.
2	Give two examples of stable molecules that represent exceptions to the octet rule (one incomplete, one expanded).	Incomplete octet: Boron trifluoride (BF3, 6 valence electrons around B); Expanded octet: Sulfur hexafluoride (SF6, 12 valence electrons around S).
3	What are resonance structures, and what is the true electronic state of a molecule displaying resonance?	Two or more valid Lewis structures representing delocalized electrons in the same atomic framework; the actual molecule is a weighted quantum mechanical resonance hybrid of all contributing forms.
4	Why is the first ionization energy of boron slightly lower than that of beryllium, despite boron having a higher nuclear charge?	Boron loses an electron from the higher-energy, more shielded 2p orbital, whereas beryllium loses an electron from a fully filled, stable 2s orbital.
5	What is electronegativity, and which chemical element has the highest electronegativity on the Pauling scale?	The relative ability of a bonded atom to attract shared electrons in a chemical bond; fluorine is highest with a Pauling value of 3.98.
6	What is the difference between an element's atomic number (Z) and its mass number (A)?	Atomic number (Z) is the number of protons and defines the element; mass number (A) is the total number of protons plus neutrons in the nucleus.
7	What is the 'electron sea model' of metallic bonding, and how does it explain electrical conductivity?	Positive metal cations are arranged in a fixed lattice surrounded by delocalized, mobile valence electrons that freely drift under an applied electric potential.
8	What are the three fundamental subatomic particles, and what are their respective charges and locations in the atom?	Protons (positive +1, nucleus), neutrons (neutral 0, nucleus), and electrons (negative -1, surrounding electron cloud).
9	What is the molecular geometry of sulfur tetrafluoride (SF4) with 5 electron domains (4 bonding, 1 lone pair)?	Seesaw (lone pair resides in the equatorial position to minimize 90-degree lone-pair/bonding-pair repulsions).
10	What is the molecular geometry of xenon tetrafluoride (XeF4) with 6 electron domains (4 bonding, 2 lone pairs)?	Square planar (the two lone pairs occupy trans axial positions 180° apart).
11	How do core electrons differ from valence electrons in chemical reactivity?	Core electrons occupy inner completed shells and do not participate in bonding; valence electrons occupy the outermost principal energy level and govern chemical bonding.
12	According to Coulomb's law, what two factors increase the lattice energy of an ionic solid?	Higher ionic charges (proportional to Q1*Q2) and smaller ionic radii (inversely proportional to interionic distance r).
13	How is formal charge calculated for an atom within a Lewis structure?	Formal Charge = (Valence electrons of free atom) - (Non-bonding valence electrons) - 1/2*(Bonding electrons).
14	What is first ionization energy, and why does it generally increase from left to right across a period?	The energy required to remove the first valence electron from an isolated gaseous atom; it increases across a period due to greater effective nuclear charge holding electrons tighter.
15	What is the fundamental principle underlying Valence Shell Electron Pair Repulsion (VSEPR) theory?	Electron pairs (bonding and non-bonding lone pairs) around a central atom repel each other electrostatically and adopt a geometry that maximizes their spatial separation.
16	What do the four quantum numbers (n, l, ml, ms) describe about an electron in an atom?	n is the principal energy level, l is the orbital angular momentum shape (s, p, d, f), ml is the spatial magnetic orientation, and ms is the electron spin (+1/2 or -1/2).
17	What are the names and group numbers of Group 1, Group 2, Group 17, and Group 18 elements?	Group 1: Alkali metals; Group 2: Alkaline earth metals; Group 17: Halogens; Group 18: Noble gases.
18	What orbital overlaps form a sigma (σ) bond versus a pi (π) bond?	Sigma bonds form from head-on (axial) end-to-end overlap of atomic/hybrid orbitals; pi bonds form from side-by-side (lateral) overlap of parallel unhybridized p orbitals.
19	What is the general periodic trend for atomic radius across a period and down a group?	Atomic radius decreases across a period (left to right) due to increasing effective nuclear charge, and increases down a group due to the addition of principal energy shells.
20	What are London dispersion forces, and what molecular property determines their strength?	Temporary induced dipole-induced dipole electrostatic attractions present in all molecules; their strength increases with greater molecular weight and electron cloud polarizability.
21	What are the electron-domain geometry and molecular geometry of ammonia (NH3)?	Electron-domain geometry is tetrahedral (4 domains); molecular geometry is trigonal pyramidal (3 bonding pairs and 1 lone pair).
22	How many sigma and pi bonds are present in a carbon-carbon triple bond (as in ethyne, C2H2)?	One sigma (σ) bond and two orthogonal pi (π) bonds.
23	How do electronegativity differences determine whether a chemical bond is nonpolar covalent, polar covalent, or ionic?	Differences < 0.4 typically yield nonpolar covalent bonds; 0.4 to ~1.7 yield polar covalent bonds; > ~1.7 yield predominantly ionic bonds.
24	What defines isotopes of a chemical element?	Atoms with identical atomic numbers (same number of protons) but different mass numbers (different numbers of neutrons).
25	What is electron affinity, and which group of elements has the most negative (exothermic) electron affinities?	The energy change occurring when an electron is added to a neutral gaseous atom; Group 17 halogens have the most exothermic electron affinities because adding one electron completes an octet.
26	What does the Aufbau principle dictate regarding electron configurations in the ground state?	Electrons fill lower-energy atomic orbitals before occupying higher-energy orbitals.
27	Why is the bond angle in water (H2O, ~104.5°) smaller than the ideal tetrahedral angle (109.5°)?	The two non-bonding lone pairs on oxygen exert greater electrostatic repulsion than bonding pairs, compressing the H-O-H bond angle.
28	What is effective nuclear charge (Zeff), and how does electron shielding influence it across a period?	Zeff is the net positive charge experienced by valence electrons (Zeff = Z - S); core shielding stays roughly constant across a period while nuclear charge increases, pulling valence electrons tighter.
29	What does the Pauli exclusion principle state concerning electrons in an atom?	No two electrons in the same atom can have the exact same set of four quantum numbers; an orbital can hold a maximum of two electrons with opposite spins.
30	According to Hund's rule, how do electrons occupy degenerate orbitals of equal energy?	Electrons singly occupy each degenerate orbital with parallel spins before any orbital is doubly occupied.
31	What orbital hybridizations correspond to linear, trigonal planar, and tetrahedral electron geometries?	Linear: sp hybridization; Trigonal planar: sp2 hybridization; Tetrahedral: sp3 hybridization.
32	What specific structural criteria are required for intermolecular hydrogen bonding to occur?	A hydrogen atom covalently bonded to a highly electronegative, small atom (N, O, or F) interacting with a lone pair on another N, O, or F atom.