- An atom with the electron configuration 1s22s22p63s23p63d54s2 has an incomplete…
- 2p sublevel
- Second principal energy level
- Third principal energy level
- 4s sublevel
The configuration is 1s22s22p63s23p63d54s2.
- \(n = 1\) has 2 electrons (full)
- \(n = 2\) has 8 electrons (full)
- \(n = 3\) can hold up to 18 electrons (3s, 3p, 3d)
Here, it has 13, so the third principal energy level is incomplete.
- What is the total number of electrons in a completely filled fourth principal level?
- 8
- 10
- 16
- 32
A completely filled level \(n\) contains \(2n^2\) electrons.
For \(n = 4\):
\(2(4^2) = 2 \times 16 = 32\)
So a full fourth principal level has 32 electrons.
- When is the characteristic bright line spectrum of an element produced?
- Its electrons form a covalent bond.
- Its electrons form an ionic bond.
- Its electrons move to a higher energy state.
- Its electrons move to a lower energy state.
A bright-line emission spectrum occurs when electrons drop to lower energy levels, releasing photons with specific energies (wavelengths). Excitation absorbs energy, while emission releases it.
- Which emanation has no mass and no charge?
- α
- β
- γ
- n0
- α: mass ≈ 4 amu, charge +2
- β: tiny mass, charge −1 or +1
- γ: mass 0, charge 0
- n0: mass ≈ 1 amu, charge 0
Only γ has no mass and no charge.
- In which system do molecule-ion attractions exist?
- NaCl(aq)
- NaCl(s)
- C6H12O6(aq)
- C6H12O6(s)
Molecule–ion attractions occur when ions in solution attract polar molecules. NaCl(aq) features Na+/Cl––H2O (dipole) interactions (ion–dipole).
- What can a particle accelerator increase the kinetic energy of?
- An α-particle and a β-particle
- An α-particle and a neutron
- A γ-ray and a β-particle
- A neutron and a γ-ray
Particle accelerators use electric fields to accelerate charged particles.
α (charge +2) and β (charge −1) can be accelerated. Neutrons (no charge) and γ-rays (photons) are not accelerated.
- What is the total number of electrons needed to completely fill all of the orbitals in an atom’s second principal energy level?
- 16
- 2
- 8
- 4
The second principal level has sublevels 2s (1 orbital) and 2p (3 orbitals).
The total number of orbitals is 4, and each holds 2 electrons. This means that it takes 8 electrons to fill all orbitals.
- An atom in an excited state can have an electron configuration of…
- 1s22s2
- 1s22p1
- 1s22s22p2
- 1s22s22p5
An excited-state configuration places one or more electrons in a higher-energy sublevel than in the ground state.
1s22p1 is excited for Li (ground state: 1s22s1).
The other options are ground-state configurations, so B is the only excited-state choice.
- Compared to the charge and mass of a proton, an electron has…
- The same charge and smaller mass
- The same charge and the same mass
- The opposite charge and smaller mass
- The opposite charge and the same mass
A proton and an electron have opposite charges (+1 vs −1). The electron’s mass is about \(\tfrac{1}{1,836}\) of a proton’s, so it has a smaller mass.
- What is the total number of sublevels in the fourth principal energy level?
- 1
- 2
- 3
- 4
The number of sublevels in principal level \(n\) equals \(n\).
For \(n = 4\), the sublevels are 4s, 4p, 4d, 4f (4 sublevels total).
- Which atom in the ground state has only one unpaired electron in its valence shell?
- Aluminum
- Silicon
- Phosphorus
- Sulfur
- Aluminum: 3s23p1 → one unpaired (p1)
- Silicon: 3s23p2 → two unpaired (Hund’s rule)
- Phosphorus: 3s23p3 → three unpaired
- Sulfur: 3s23p4 → two unpaired (one pair + two singles)
So aluminum has exactly one unpaired valence electron.
- Which of the following best describes the shape and bonding of a diatomic bromine molecule?
- Symmetrical and polar
- Symmetrical and nonpolar
- Asymmetrical and polar
- Asymmetrical and nonpolar
Br2 is a diatomic molecule of identical atoms. The bond is nonpolar covalent, the molecule is linear and symmetrical, so overall it is nonpolar.
- What is the oxidation number of sulfur in H2SO4?
- 0
- -2
- +6
- +4
Let oxidation states sum to 0 in H2SO4.
\(H = +1\)
\(O = −2\)
Let \(S = x\):
\(x + 2 + (-8)\) \(= 0 \Rightarrow x – 6 = 0 \Rightarrow x\) \(= +6\)
Therefore, sulfur is +6.
- When α-particles are used to bombard gold foil, most of the α-particles pass through undeflected. This result indicates that most of the volume of a gold atom consists of what?
- Neutrons
- Protons
- Deuterons
- Unoccupied space
Rutherford’s gold-foil experiment showed most α-particles passed through undeflected, indicating the atom is mostly empty (unoccupied) space with a small, dense, positively charged nucleus.
- When an α-particle is emitted by an atom, what happens to the atomic number of the atom?
- It decreases by 2
- It increases by 2
- It decreases by 4
- It increases by 4
An α-particle is a 42He nucleus. Emitting, it reduces the mass number by 4 and the atomic number by 2.
- Which of the following elements has the corresponding valence subshell of 3p4?
- Aluminum
- Silicon
- Sulfur
- Chlorine
Valence 3p4 corresponds to sulfur.
- Which of the following elements has the corresponding valence subshell of 3p6?
- Sulfur
- Chlorine
- Argon
- Potassium
Valence 3p6 is a closed p subshell → argon (noble gas).
- Which of the following elements has the corresponding valence subshell of 3s1?
- Neon
- Sodium
- Magnesium
- Aluminum
Valence 3s1 is sodium (Na).
- Which of the following elements has the corresponding valence subshell of 2p4?
- Nitrogen
- Oxygen
- Neon
- Magnesium
Valence 2p4 corresponds to oxygen.
- What is the maximum number of electrons that can be found in the f orbital?
- 2
- 4
- 6
- 8
An orbital can hold at most two electrons with opposite spins. The f here names the orbital’s type (ℓ = 3), not the whole subshell. Larger numbers like 4, 6, or 8 would require multiple f orbitals.