Atomic Structure and Isotopes
What subatomic particle determines the identity of an element?
Protons (atomic number = identity)
What are the horizontal rows and vertical columns on the periodic table called?
Rows = periods, Columns = groups/families
Write the electron configuration of oxygen (O).
1s² 2s² 2p⁴
What particle is emitted in alpha decay?
Alpha particle (⁴₂He)
Write the chemical formula for magnesium phosphate.
Sodium oxide
An atom has 20 protons, 20 neutrons, and 18 electrons. What is its ion symbol?
Ca²⁺
Which element is more metallic: Na or Mg?
Na (further left = more metallic)
What is the noble gas configuration of calcium (Ca)?
[Ar] 4s²
Write the balanced nuclear equation for uranium-238 undergoing alpha decay.
²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He
Name the compound FeCl₃ (include the Roman numeral).
Mg₃(PO₄)₂
Write the isotope symbol for an atom with 17 protons and 18 neutrons.
³⁵₁₇Cl
Rank these atoms in order of increasing atomic size: O, F, N, S, Mg.
F < O < N < S < Mg
Which element has the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁴?
Sulfur (S)
What happens in beta decay, and how does the atomic number change?
Neutron → proton + e⁻; atomic number +1
Write the chemical formula for ammonium carbonate.
Iron(III) chloride
Calculate the average atomic mass of chlorine if 75.77% is Cl-35 (34.969 amu) and 24.23% is Cl-37 (36.966 amu).
35.45 amu
Which has the larger radius — Na or Na⁺? Explain why.
Na (neutral atom) — Na⁺ loses an electron, smaller radius
How many unpaired electrons are in a nitrogen atom?
3 unpaired (in 2p³)
Define nuclear fission and fusion, and give one real-world example of each.
Fission = splitting nucleus (nuclear reactors). Fusion = combining nuclei (sun, H-bomb).
Write the chemical formula for ammonium carbonate.
(NH₄)₂CO₃
A mystery element has two isotopes: X-10 (10.013 amu, 19.91%) and X-11 (11.009 amu, 80.09%). Calculate its average atomic mass and identify the element.
10.81 amu, element = Boron (B)
Explain why ionization energy increases across a period but decreases down a group.
Across: more protons → stronger attraction. Down: more shells → weaker attraction.
Explain the difference between the 3s and 4s orbitals in terms of energy and distance from the nucleus.
Both are s-orbitals; 4s has higher energy & farther from nucleus
Balance this nuclear equation and identify the missing particle: ¹⁴₆C → ¹⁴₇N + ?
Missing particle: β⁻ (⁰₋₁e)
Name the compound P₄O₁₀ (use correct molecular prefixes).
Tetraphosphorus decoxide (often called phosphorus pentoxide)