Theory — Reactions, Balancing, and Bonding
Combination Reactions
In a combination (synthesis) reaction, two or more elements join to form a single compound. The ratio in which they combine is set by the charges (for ionic compounds) or the shared electrons (for covalent compounds). For example, calcium and oxygen combine to form calcium oxide, CaO.
Balancing Equations
A balanced equation has the same number of each kind of atom on both sides — mass is conserved. We balance by placing coefficients in front of formulas; we never change subscripts, because that would change the substance. Remember that several elements occur as diatomic molecules: H₂, O₂, N₂, F₂, Cl₂, Br₂, I₂.
balanced: 2 H₂ + 1 O₂ → 2 H₂O
Left: H = 4, O = 2 · Right: H = 4, O = 2
Ionic vs Covalent Bonds
A metal + non-metal typically forms an ionic compound (electrons transferred, named with the metal then the non-metal as an -ide). Two non-metals form a covalent compound (electrons shared).
Ionic
Metal + non-metal. Electrons transferred. e.g. CaO, LiBr, MgF₂, ZnCl₂.
Covalent
Non-metal + non-metal. Electrons shared. e.g. NH₃, H₂O, CO.
Conservation
Atoms are neither created nor destroyed — coefficients make both sides equal.
| Combination | Product | Bond type |
|---|---|---|
| Ca + O | CaO (calcium oxide) | ionic |
| N + 3H | NH₃ (ammonia) | covalent |
| 2H + O | H₂O (water) | covalent |
| Mg + 2F | MgF₂ (magnesium fluoride) | ionic |
Apparatus
The equipment a real reaction-types experiment uses. In the simulation these are modelled for you, but the readings correspond to what each instrument would measure.
Instructions — Running the Virtual Experiment
This activity supports the Week 5 research lab. The simulation is for practice and to build understanding; your full research (element data, electronic configurations, periodic-table positions, and uses) is done as described in the assignment. Record your practice work and screenshots in your lab report.
Simulation — Balancing and Combination Reactions
Left side (reactants)
Right side (products)
Choose an equation
Choose a combination
Team Questions
Example Lab Report
This is a research lab. The sample below shows the expected format for one combination; in your full report, work through each element set as described in the assignment, including names, atomic numbers, electronic configurations, periodic-table positions, particle counts, balanced equations, and uses.
Chemical Reactions and Activity Series
Chemistry | Section: [Your Section] | Date: [Date]
Lab Members: [Names of all members present]
Title
Combination reactions of element pairs: products, balanced equations, bonding, and uses.
Method
For each element set, information was researched from reputable chemistry references on the web. The virtual lab was used for practice — balancing equations and confirming products and bond types. Screenshots of the practice simulation are included where relevant.
Results and Calculations (worked example: Ca with O)
Elements: Calcium (Ca) and Oxygen (O).
Calcium: atomic number 20, atomic mass 40.08, Group 2, Period 4; electronic configuration 2, 8, 8, 2; 20 protons, 20 electrons, 20 neutrons (in Ca-40).
Oxygen: atomic number 8, atomic mass 16.00, Group 16, Period 2; electronic configuration 2, 6; 8 protons, 8 electrons, 8 neutrons (in O-16).
Compound formed: calcium oxide, CaO (ionic — metal + non-metal).
Uses: calcium oxide (quicklime) is used in cement and mortar, in steelmaking, and as a drying agent.
Discussion / Conclusions
Each combination pairs the elements in the ratio set by their combining capacities, and the balanced equations confirm conservation of mass. Ionic products formed between metals and non-metals (e.g. CaO, LiBr, MgF₂, ZnCl₂), while covalent products formed between non-metals (e.g. NH₃, H₂O, CO). The compounds have wide practical uses — for instance ammonia in fertilisers, water as a universal solvent, and zinc chloride as a soldering flux.
Practice Questions
Show all work. Remember diatomic elements (H₂, O₂, N₂, F₂, Cl₂, Br₂) and balance with coefficients only.