Atomic Structure & Periodic Table
True/False
All isotopes of an element have the same number of neutrons.
False
Isotopes have the same number of protons but different numbers of neutrons, which gives them different mass numbers.
True/False
Ionic bonds form between two non-metals.
False
Ionic bonds form between a metal and a non-metal, where electrons are transferred. Two non-metals typically form covalent bonds.
True/False
All acids contain hydrogen ions in aqueous solution.
True
Acids release H⁺ ions in water, which is the defining property of acids according to the Arrhenius theory.
True/False
Alkanes are unsaturated hydrocarbons.
False
Alkanes are saturated hydrocarbons — they contain only single bonds between carbon atoms. Unsaturated hydrocarbons (alkenes, alkynes) have double or triple bonds.
True/False
Carbon monoxide is harmless because it is colorless and odorless.
False
Carbon monoxide (CO) is dangerous precisely because it’s colorless and odorless. It binds to hemoglobin more strongly than oxygen, reducing oxygen transport in the body.
MCQ
Which subatomic particle determines the identity of an element?
A. Neutron
B. Electron
C. Proton
D. Nucleon
C. Proton
The number of protons (atomic number) defines the element. For example, carbon always has 6 protons.
MCQ
Which of the following compounds contains covalent bonds?
A. NaCl
B. MgO
C. CO₂
D. KBr
C. CO₂
Carbon dioxide (CO₂) is formed by sharing electrons between non-metals — a covalent bond.
MCQ
Which of the following is a weak acid?
A. HCl
B. H₂SO₄
C. CH₃COOH
D. HNO₃
C. CH₃COOH
Acetic acid (CH₃COOH) only partially ionizes in water, making it a weak acid. The others are strong acids.
Fill in the Blanks
The functional group in alcohols is the ___ group.
A. hydroxyl
B. carboxyl
C. alkyl
D. amino
A. hydroxyl
Alcohols contain the hydroxyl group (-OH), which makes them polar and capable of hydrogen bonding.
MCQ
Which process removes carbon dioxide from the atmosphere?
A. Respiration
B. Combustion
C. Photosynthesis
D. Fermentation
C. Photosynthesis
Photosynthesis by plants absorbs CO₂ and releases oxygen, helping regulate atmospheric carbon.
Fill in the Blanks
The mass number of an atom is the sum of protons and ___.
A. neutrons
B. electrons
C. nucleons
D. atoms
A. neutrons
Mass number = protons + neutrons. Electrons have negligible mass.
Fill in the Blanks
In an ionic bond, electrons are ___ from one atom to another.
A. transferred
B. shared
C. lost
D. created
A. transferred
Ionic bonding involves transfer of electrons from a metal to a non-metal, forming oppositely charged ions.
MCQ
Which salt is formed when hydrochloric acid reacts with sodium hydroxide?
A. Sodium chloride
B. Sodium sulfate
C. Sodium nitrate
D. Sodium carbonate
A. Sodium chloride
HCl + NaOH → NaCl + H₂O. This is a neutralization reaction.
MCQ
Which compound is formed when ethanol is oxidized?
A. Ethene
B. Ethanoic acid
C. Methanol
D. Propanol
B. Ethanoic acid
Oxidation of ethanol (CH₃CH₂OH) produces ethanoic acid (CH₃COOH) — a carboxylic acid.
Fill in the Blanks
The greenhouse effect is caused by gases that trap ___ radiation.
A. infrared
B. ultraviolet
C. gamma
D. visible
A. infrared
Infrared radiation is trapped by greenhouse gases like CO₂ and CH₄, warming the Earth’s surface.
MCQ
Which element is most reactive in Group I?
A. Lithium
B. Sodium
C. Potassium
D. Cesium
D. Cesium
Cesium is the most reactive because reactivity increases down the group due to weaker attraction between nucleus and outer electron.
MCQ
Which element is most likely to form a triple covalent bond?
A. Hydrogen
B. Nitrogen
C. Oxygen
D. Fluorine
B. Nitrogen
Nitrogen has five valence electrons and often shares three pairs to complete its octet — forming a triple bond in N₂.
Fill in the Blanks
The pH scale ranges from ___ to 14.
A. 0
B. 1
C. -1
D. 2
A. 0
The pH scale typically ranges from 0 (strong acid) to 14 (strong base).
Fill in the Blanks
The process of breaking down large hydrocarbons into smaller ones is called ___.
A. cracking
B. polymerization
C. combustion
D. distillation
A. cracking
Cracking breaks long-chain hydrocarbons into smaller, more useful molecules like alkenes and fuels.
True/False
Methane is less effective than carbon dioxide at trapping heat.
False
Methane (CH₄) is more potent than CO₂ in trapping heat, though it’s present in smaller quantities.
True/False
Noble gases are reactive because they have full outer shells.
False
Noble gases are unreactive because their outer shells are full — they are chemically stable.
True/False
Ionic compounds have low melting points due to weak electrostatic forces.
False
Ionic compounds have high melting points because of strong electrostatic attraction between oppositely charged ions.
MCQ
Which of the following is an example of a basic oxide?
A. CO₂
B. Na₂O
C. SO₂
D. NO₂
B. Na₂O
Sodium oxide (Na₂O) reacts with water to form NaOH, a base — hence it’s a basic oxide.
Fill in the Blanks
The simplest alkane is ___, with the formula CH₄.
A. methane
B. ethane
C. propane
D. butane
A. methane
Methane is the simplest alkane — one carbon atom bonded to four hydrogen atoms.
MCQ
Which gas is primarily responsible for acid rain?
A. CO₂
B. SO₂
C. CH₄
D. O₂
B. SO₂
Sulfur dioxide (SO₂) reacts with water in the atmosphere to form sulfuric acid, contributing to acid rain.