Atomic Structure and Chemical Bonding

Flashcards covering key concepts in atomic structure, chemical bonding, molecular shapes, and intermolecular forces.

What are the three subatomic particles that make up an atom?

Protons, Neutrons, and Electrons

What is the relative mass of a proton and neutron?

Approximately 1

What is the relative charge of a proton, neutron, and electron?

+1, 0, and -1 respectively

What is the atomic number (Z) of an atom?

The number of protons in the nucleus of an atom

What is the mass number (A) of an atom?

The total number of protons and neutrons in the nucleus of an atom

How do you calculate the number of neutrons in an atom?

Mass number (A) - Atomic number (Z)

Where is the mass of an atom concentrated?

In the nucleus, due to the presence of protons and neutrons

How do electrons behave in an electric field?

Electrons are deflected away from the negative plate and towards the positive plate because they are negatively charged and have a small mass.

How do protons behave in an electric field?

Protons are deflected away from the positive plate and towards the negative plate because they are positively charged and heavier than electrons.

How do neutrons behave in an electric field?

Neutrons are not deflected at all because they are neutral in character.

What happens to an atom when it gains or loses electrons?

It forms an ion, becoming charged.

What is the relationship between the number of protons and electrons in a neutral atom?

The number of protons equals the number of electrons.

What is an isotope?

Atoms of the same element that contain the same number of protons and electrons but a different number of neutrons

What is the chemical property of isotopes?

Same chemical characteristics since they have the same number of electrons in their outer shells.

What is the trend in atomic radius across a period in the periodic table?

Atomic radius generally decreases across a period due to increasing nuclear charge and the addition of electrons to the same principal quantum shell.

What is the trend in atomic radius down a group in the periodic table?

Atomic radius generally increases down a group due to the addition of electron shells and increased shielding.

How does gaining electrons affect ionic radius?

Ionic radius increases with increasing negative charge because the outermost electrons are further away from the positively charged nucleus.

How does losing electrons affect ionic radius?

Ionic radius decreases with increasing positive charge because there are fewer electrons experiencing a greater electrostatic force of attraction to the nucleus.

Define 'electronic configuration'.

The arrangement of electrons in an atom around the nucleus in principal energy levels or principal quantum shells, split into subshells (s, p, d, f).

What is the maximum number of electrons each principal quantum shell can hold?

n=1: up to 2 electrons, n=2: up to 8 electrons, n=3: up to 18 electrons, n=4: up to 32 electrons

What is the order of increasing energy for subshells?

s < p < d < f, but the 4s orbital is filled before the 3d orbital.

What are Orbitals?

Orbitals exist at specific energy levels, electrons can only be found at these levels, and each orbital can be occupied by a maximum of 2 electrons.

What is 'ground state'?

The most stable electronic configuration of an atom which has the lowest amount of energy, achieved by filling the subshells of energy with the lowest energy first (1s)

What are the shapes of s and p orbitals?

s orbitals are spherical, and p orbitals are dumbbell-shaped, oriented along the x, y, and z axes.

What is spin-pair repulsion and how does it influence electron configuration?

Electrons with similar spin repel each other. Therefore, electrons will occupy separate orbitals in the same subshell to minimize this repulsion and have their spin in the same direction.

What is a 'free radical'?

Species with one or more unpaired electron.

How are ions formed and how does the electron configuration differ in positive and negative ions compared to their neutral atoms?

Ions are formed when atoms lose or gain electrons. Positive ions lose electrons, and negative ions gain electrons, resulting in a different number of electrons compared to their atomic number.

What are the 4 main blocks in the Periodic Table concerning electronic configuration?

s block elements (valence electrons in an s orbital), p block elements (valence electrons in a p orbital), d block elements (valence electrons in a d orbital), and f block elements (valence electrons in an f orbital).

Define ionization energy (IE).

The amount of energy required to remove one mole of electrons from one mole of gaseous atoms of an element to form one mole of gaseous ions.

What are the four factors that affect ionization energy?

The size of the nuclear charge, the distance of outer electrons from the nucleus, the shielding effect of inner electrons, and spin-pair repulsion.

What is electronegativity?

Electronegativity is the ability of an atom to attract a pair of electrons towards itself in a covalent bond.

What is the Pauling scale?

The Pauling Scale assigns Electronegativity each atom. Fluorine is the most electronegative atom on the Periodic Table, with a value of 4.0

How does nuclear attraction affect electronegativity?

Attraction exists between the positively charged protons in the nucleus and negatively charged electrons. An increase in the number of protons leads to an increase in nuclear attraction for the electrons in the outer shells. Therefore, an increased nuclear charge results in an increased electronegativity.

How does atomic radius affect electronegativity?

Electrons closer to the nucleus are more strongly attracted towards its positive nucleus. Those electrons further away from the nucleus are less strongly attracted towards the nucleus. Therefore, an increased atomic radius results in a decreased electronegativity.

Describe the trend in electronegativity across a Period in the Periodic Table.

Electronegativity increases across a Period due to increasing nuclear charge and decreasing atomic radii.

Describe the trend in electronegativity down a Group in the Periodic Table.

Electronegativity decreases down a Group due to increased shielding and increasing atomic radii.

What types of elements are involved in ionic bonding?

Ionic bonding involves the transfer of electrons, typically from a metal to a nonmetal.

How do ionic compounds form a lattice structure?

Ions in a lattice are arranged in a regular repeating pattern, so that positive charges cancel out negative charges. The attraction between the cations and anions is occuring in all directions.

What causes high melting points in ionic compounds?

The strong electrostatic forces between oppositely charged ions require a large amount of energy to overcome, which is why ionic compounds have high melting points.

What is metallic bonding?

The electrostatic attraction between positively charged metal ions and a 'sea' of delocalized electrons.

How does electron sharing lead to covalent bond formation?

Sharing electrons in the covalent bond allows each of the two atoms to achieve an electron configuration similar to a noble gas.

Briefly explain how a dative covalent bond (coordinate bond) forms.

One atom provides both electrons to form a bond with an electron-deficient atom, which has an unfilled outer orbital.

What is the difference between a sigma (σ) bond and a pi (π) bond?

Sigma (σ) bonds are formed by direct overlap of orbitals between the bonding atoms, while Pi (π) bonds are formed by the sideways overlap of adjacent p orbitals above and below the σ bond.

Define bond energy.

The bond energy is the energy required to break one mole of a particular covalent bond in the gaseous state.

Define bond length.

The bond length is the internuclear distance of two covalently bonded atoms; it's the distance from the nucleus of one atom to another atom in a covalent bond.

State the general relationship between bond length, bond strength, and number of bonds (single, double, triple).

Triple bonds are the shortest and strongest covalent bonds, due to the large electron density between the nuclei.

What is VSEPR theory?

The valence shell electron pair repulsion theory predicts the shape and bond angles of molecules based on minimizing repulsion between electron pairs around a central atom.

How do lone pairs affect molecular shape?

Lone pairs of electrons repel each other and bonding pairs more strongly than bonding pairs repel each other, influencing bond angles and molecular shapes.

What conditions are necessary for hydrogen bonding to occur?

A species must have an O or N atom with an available lone pair of electrons and a species with an -OH or -NH group.

How does hydrogen bonding affect the properties of water?

Causes anomalous properties such as high melting and boiling points, high surface tension, and lower density of ice compared to liquid water.

What is a dipole moment and how is it represented?

A measure of how polar a bond is. The direction of the dipole moment is shown by the following sign ⟶, in which the arrow points to the partially negatively charged end of the dipole.

What is the difference between intramolecular and intermolecular forces?

Intramolecular forces are forces within a molecule (e.g., ionic, covalent, metallic bonding), whereas intermolecular forces are forces between molecules (van der Waals forces).

List the intermolecular forces in order of increasing strength.

London dispersion forces < permanent dipole-permanent dipole forces < hydrogen bonding

What is the relationship between enthalpy change and exothermic/endothermic reactions?

Exothermic reactions have a negative enthalpy change (heat is released), while endothermic reactions have a positive enthalpy change (heat is absorbed).

How do you calculate partial pressure of a gas in a mixture?

Partial pressure = (mole fraction of gas) x (total pressure)

What does 'OIL RIG' stand for in redox reactions?

Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons)

How can you identify a redox reaction?

Look for changes in oxidation numbers of elements during the reaction.

What are spectator ions in a redox reaction?

Ions that do not participate in the redox reaction and remain unchanged in the solution.

How does a catalyst affect equilibrium?

A catalyst speeds up both forward and reverse reactions equally, thus reaching equilibrium faster but not changing the position of the equilibrium.

What factors affect the rate of a chemical reaction?

Temperature, concentration, surface area, catalysts, and pressure (for gases).

How does increasing temperature affect the equilibrium constant (K)?

For endothermic reactions, increasing temperature increases K. For exothermic reactions, increasing temperature decreases K.

What is the effect of pressure on equilibrium involving gases?

Increasing pressure shifts the equilibrium towards the side with fewer moles of gas.

How is K_p (equilibrium constant in terms of partial pressures) calculated?

K_p = (Partial pressure of products) / (Partial pressure of reactants), each raised to the power of their stoichiometric coefficients.

Describe the role of equilibrium in the Haber process.

Optimizing conditions (pressure, temperature) to maximize ammonia yield, balancing rate and equilibrium considerations.

What is the role of a catalyst in industrial processes like the Haber process?

Increases the rate of reaction without being consumed, allowing equilibrium to be reached faster.

Compare strong acids/bases to weak acids/bases in terms of ionization.

Strong acids/bases completely ionize in solution, while weak acids/bases only partially ionize.

What is the conjugate acid-base pair?

Two species that differ by the presence of a proton (H^+).

What is the relationship between Ka and pKa?

pKa = -log_{10}(Ka); smaller pKa indicates a stronger acid.

What is a buffer solution?

A solution that resists changes in pH upon addition of small amounts of acid or base. It contains a weak acid and its conjugate base, or a weak base and its conjugate acid.

What is the Henderson-Hasselbalch equation?

pH = pKa + log_{10}([A^-]/[HA]), where [A-] is the concentration of the conjugate base and