ACT SSC Chemistry · Unit 1
ACT SSC Chemistry Unit 1: Chemical Fundamentals — Flashcards & Quiz
ACT SSC Chemistry Unit 1 covers chemical fundamentals within the BSSS framework. This unit explores atomic structure, electron configuration, the periodic table, chemical bonding, stoichiometry and the mole concept. These flashcards and quiz questions help you revise the foundational chemistry concepts tested in ACT assessments.
Key Terms
- Electron Configuration
- The arrangement of electrons in an atom's energy levels and subshells, determining chemical reactivity and bonding behaviour; writing configurations is a core skill in BSSS Chemistry Unit 1 assessments.
- Ionic Bonding
- The electrostatic attraction between oppositely charged ions formed by the transfer of valence electrons from a metal to a non-metal; assessed through lattice structure and property questions in ACT SSC Chemistry.
- Covalent Bonding
- A chemical bond formed by the sharing of one or more pairs of electrons between non-metal atoms; BSSS assessments require Lewis structures and VSEPR shape predictions for covalent molecules.
- Electronegativity
- A measure of an atom's ability to attract bonding electrons towards itself in a covalent bond; understanding electronegativity trends across the periodic table is essential for BSSS polarity questions.
- Periodic Trend
- A predictable pattern in atomic properties such as atomic radius, ionisation energy and electronegativity across periods and down groups; BSSS unit score tasks require explanation of trends using atomic structure.
- VSEPR Theory
- Valence Shell Electron Pair Repulsion theory predicts molecular shape by minimising repulsion between electron pairs around the central atom; a key tool for ACT SSC molecular geometry questions.
- Metallic Bonding
- The bonding model in which a lattice of positive metal ions is held together by a sea of delocalised electrons, explaining properties like conductivity and malleability; assessed in BSSS structure-property tasks.
Sample Flashcards
Q1: Outline the key features of the Bohr model of the atom.
The Bohr model places electrons in fixed circular orbits (energy levels/shells) around the nucleus. Electrons occupy the lowest available energy level and can jump between levels by absorbing or emitting a specific quantum of energy.
Q2: What are the three subatomic particles and their properties?
Protons: positive charge (+1), mass ≈ 1 amu, in the nucleus. Neutrons: no charge (0), mass ≈ 1 amu, in the nucleus. Electrons: negative charge (−1), mass ≈ 1/1836 amu, in electron shells.
Q3: Write the electron configuration for sodium (Na, Z = 11).
Na: 1s² 2s² 2p⁶ 3s¹ (or 2, 8, 1 in shell notation). Sodium has 11 electrons filling orbitals in order of increasing energy using the aufbau principle.
Q4: What is the aufbau principle?
The aufbau principle states that electrons fill orbitals in order of increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on. Lower-energy orbitals are filled before higher-energy ones.
Q5: How does electronegativity change across a period and down a group?
Electronegativity increases across a period (left to right) due to increasing nuclear charge with similar shielding. It decreases down a group because increased atomic radius and electron shielding reduce the nucleus’s pull on bonding electrons.
Q6: How does ionisation energy change across a period and down a group?
First ionisation energy increases across a period (greater nuclear charge holds electrons more tightly). It decreases down a group (valence electrons are further from the nucleus with more shielding).
Q7: How does atomic radius change across a period and down a group?
Atomic radius decreases across a period (increasing nuclear charge pulls electrons closer). It increases down a group (each period adds a new electron shell, increasing distance from the nucleus).
Q8: Describe ionic bonding and give an example.
Ionic bonding involves the transfer of electrons from a metal to a non-metal, forming oppositely charged ions (cations and anions) held together by electrostatic attraction in a crystal lattice.
Sample Quiz Questions
Q1: The Bohr model places electrons in a cloud of probability around the nucleus.
Answer: FALSE
The Bohr model uses fixed circular orbits. The quantum mechanical model uses probability clouds (orbitals).
Q2: The mass of an electron is approximately equal to the mass of a proton.
Answer: FALSE
An electron has about 1/1836 the mass of a proton. Protons and neutrons have approximately equal mass.
Q3: According to the aufbau principle, the 4s orbital fills before the 3d orbital.
Answer: TRUE
The 4s orbital has lower energy than 3d and fills first according to the aufbau principle.
Q4: Electronegativity decreases across a period from left to right.
Answer: FALSE
Electronegativity INCREASES across a period due to increasing nuclear charge with similar shielding.
Q5: Atomic radius increases down a group.
Answer: TRUE
Each period adds a new electron shell, increasing the distance of valence electrons from the nucleus.
Why It Matters
Chemical fundamentals in ACT SSC Chemistry Unit 1 provides the foundational framework for understanding all chemical behaviour. BSSS assessments test your ability to explain electron configurations, predict bonding types, perform stoichiometric calculations, and relate atomic properties to position on the periodic table. This unit establishes the conceptual vocabulary and reasoning patterns used throughout the entire chemistry course. Students who build a thorough understanding of why atoms bond as they do and how to use the mole concept for quantitative analysis find that subsequent units on molecules, equilibrium, and structure become significantly more intuitive. Electron configuration and periodic trends underpin the molecules unit, where bonding type and molecular polarity depend on electronegativity differences established here. BSSS exam questions on chemical fundamentals commonly require you to link electron configuration to an element's reactivity or bonding behaviour, so practise writing configurations and predicting properties for unfamiliar elements using periodic trends.
Key Concepts
Atomic Structure and the Mole Concept
Understanding atomic number, mass number, isotopes, electron configuration, and the mole concept forms the basis for predicting chemical properties and performing quantitative analysis. BSSS assessments frequently test configuration writing, stoichiometric calculations and their connection to periodic trends.
Periodic Table Trends
Atomic radius, ionisation energy, electronegativity, and electron affinity vary predictably across periods and down groups. Understanding the physical reasons behind these trends allows you to predict properties of unfamiliar elements and explain observed chemical behaviour.
Chemical Bonding
Ionic, covalent, and metallic bonding arise from different electron interactions between atoms. Being able to predict bond type from electronegativity differences, draw Lewis structures, and explain how bonding determines physical properties is central to BSSS assessments.
Molecular Shape and Polarity
VSEPR theory predicts molecular geometry from electron pair repulsion around a central atom. Understanding how molecular shape determines polarity, and how polarity influences intermolecular forces and physical properties, connects atomic-level structure to macroscopic behaviour.
Common Mistakes to Avoid
- Writing electron configurations that violate the Aufbau principle or Hund's rule — BSSS Chemistry examiners check that electrons fill orbitals in order of increasing energy and that degenerate orbitals are singly occupied first.
- Assuming all covalent compounds are molecular — ACT SSC assessments also test covalent network solids like diamond and silicon dioxide, which have very different properties from simple molecular substances.
- Describing ionic bonds as the transfer of electrons without mentioning the resulting electrostatic attraction between ions — ACT Board of Senior Secondary Studies marking guides require both the transfer and the attraction for full marks.
- Confusing intermolecular forces with intramolecular bonds in ACT SSC property questions — boiling point depends on intermolecular forces between molecules, not the covalent bonds within them.
Study Tips
- Practise writing electron configurations for elements across all blocks of the periodic table until the process becomes automatic.
- Create flashcards for periodic trends with the physical explanation for each trend, using spaced repetition for lasting understanding.
- Draw Lewis structures for ten molecules daily, checking each against VSEPR predictions for shape and polarity.
- Build a summary table connecting bond type to properties like melting point, conductivity, and solubility to prepare for comparison questions.
- Use the periodic table actively during study — trace trends with your finger while explaining them aloud to reinforce spatial patterns.
- Before your exam, work through the practice questions in this set at least twice using spaced repetition. Testing yourself repeatedly is the most effective revision strategy for long-term retention.
Related Topics
Frequently Asked Questions
What does ACT SSC Chemistry Unit 1 cover?
Unit 1 covers chemical fundamentals including atomic structure, electron configuration, the periodic table, stoichiometry, the mole concept, chemical bonding, Lewis structures, VSEPR theory and intermolecular forces.
How many flashcards are in this set?
This free set contains 20 flashcards and 20 true/false quiz questions covering all key concepts in Unit 1, aligned to the BSSS Chemistry framework.
Are these flashcards aligned to the ACT curriculum?
Yes — every flashcard and quiz question is mapped to the BSSS Science Framework for ACT SSC Chemistry Unit 1.
Last updated: March 2026 · 20 flashcards · 20 quiz questions · Content aligned to the BSSS Framework