Isotopes
What are isotopes?
Atoms of the same element with different numbers of neutrons, giving them different mass numbers.
What is the maximum number of electrons that can fit in an s, p, and d orbital?
s = 2, p = 6, d = 10.
What are the three subatomic particles in an atom?
Protons, neutrons, and electrons.
What is a chemical bond, and why do atoms form bonds?
A chemical bond is an attraction between atoms. Atoms form bonds to achieve a full valence shell (stability).
What is electronegativity, and how does it change across a period and down a group?
Electronegativity is an atom's ability to attract electrons in a bond. Increases across a period, decreases down a group.
Explain why isotopes of an element have different mass numbers but the same chemical properties.
Same number of protons and electrons, so their chemical behaviour remains unchanged, but mass varies due to neutron differences.
Write the full electron configuration for oxygen (O).
1s² 2s² 2p⁴.
Define atomic number and mass number.
Atomic number = Number of protons in an atom. Mass number = Sum of protons and neutrons in the nucleus.
Describe the difference between ionic and covalent bonds.
Ionic bonds = Transfer of electrons (metal + non-metal). Covalent bonds = Sharing of electrons (non-metal + non-metal).
Which element has a larger atomic radius, lithium (Li) or fluorine (F)? Why?
Lithium (Li). Atomic radius decreases across a period because of increasing nuclear charge pulling electrons closer.
A sample contains 75% Cl-35 and 25% Cl-37. Calculate the relative atomic mass of chlorine.
(0.75 × 35) + (0.25 × 37) = 35.5 amu.
What is the condensed electron configuration for calcium (Ca)?
[Ar] 4s².
How many protons, neutrons, and electrons are in a sulfur-32 (³²S) atom?
Protons: 16, Neutrons: 16, Electrons: 16
Why do noble gases rarely form chemical bonds?
They have a full valence shell, making them chemically stable.
Order the following elements from lowest to highest first ionization energy: Na, Mg, Cl.
Na < Mg < Cl. Ionization energy increases across a period as the nuclear attraction increases.
Carbon-14 is a radioactive isotope used in carbon dating. What makes it different from carbon-12?
Carbon-14 has 8 neutrons, while carbon-12 has 6 neutrons. C-14 is radioactive, C-12 is stable.
Identify the valence electrons in phosphorus (P) and explain their role in bonding.
5 valence electrons (in the 3s²3p³ orbital). Valence electrons determine bonding capacity.
Explain the difference between ions and neutral atoms in terms of protons and electrons.
Neutral atoms have equal protons and electrons. Ions have an unequal number: Cations (+) lose electrons, Anions (-) gain electrons.
Which type of bond forms when electrons are transferred from one atom to another?
Ionic bond.
Explain why group 1 elements (alkali metals) are more reactive as you go down the group.
Lower ionization energy makes it easier to lose an electron, increasing reactivity.
An unknown element has three naturally occurring isotopes with the following masses and abundances: 62.93 amu (69.17%), 64.93 amu (30.83%). Identify the element.
Using the formula: (62.93 × 0.6917) + (64.93 × 0.3083) = 63.55 amu, which corresponds to Copper (Cu).
Why are chromium (Cr) and copper (Cu) exceptions to the standard electron configuration rules?
They promote an s electron to the d orbital to achieve a more stable half-filled or fully filled d-subshell.
How do scientists use isotopes in medicine and industry? Provide one example for each.
Medicine: Radioisotopes (e.g., Technetium-99m) are used in imaging scans to diagnose diseases. Industry: Carbon-14 dating determines the age of ancient fossils.
Predict whether the bond in NaCl (sodium chloride) is ionic, polar covalent, or non-polar covalent. Explain your reasoning.
Ionic bond – Sodium (Na) donates an electron to chlorine (Cl), forming Na⁺ and Cl⁻ ions.
Why does fluorine have the highest electronegativity of all elements?
Fluorine has a small atomic radius and a strong nuclear charge, making it highly attractive to electrons.