C1 Flashcards
Define an atom.
The smallest particle of an element that retains its chemical properties.
Define an element.
A substance made of only one type of atom (e.g.
Define a compound.
Two or more elements chemically bonded (e.g.
What distinguishes a mixture from a compound?
Mixtures are physically combined; compounds are chemically bonded.
Name 4 separation techniques.
Filtration, crystallization, distillation, chromatography
When is fractional distillation used?
To separate liquids with similar boiling points (e.g., ethanol/water)
What did Rutherford’s alpha scattering experiment show?
Most atoms are empty space; mass is concentrated in a nucleus.
Describe Dalton’s atomic model.
Atoms are solid indivisible spheres
How did Mendeleev arrange the periodic table?
By atomic weight, leaving gaps for undiscovered elements.
Modern periodic table order.
By atomic number (number of protons).
Charge/mass of a proton.
+1 charge; mass = 1
Charge/mass of a neutron.
0 charge; mass = 1
Charge/mass of an electron.
-1 charge; negligible mass (≈1/1836)
Atomic number definition.
Number of protons in an atom.
Mass number definition.
Protons + neutrons in an atom.
Isotopes definition.
Atoms of the same element with different numbers of neutrons.
Calculate relative atomic mass (Aᵣ).
Aᵣ = (isotope1 × %1) + (isotope2 × %2) / 100 (e.g., Cl: 35.5)
Electronic structure of sulfur (atomic number 16).
2,8,6
Group number vs. electrons in outer shell.
Group number = number of outer electrons (for Groups 1
Period number meaning.
Number of electron shells.
Properties of metals.
Conductors, malleable, form positive ions
Properties of non-metals.
Poor conductors, brittle, form negative ions
Group 0 elements name and reactivity.
Noble gases; unreactive (full outer shell)
Trend in noble gas boiling points.
Increases down the group (e.g.
Use of argon.
Inert atmosphere in lightbulbs.
Group 1 trend in reactivity.
Increases down the group (outer electron further from nucleus)
Reaction: Sodium + water.
Sodium hydroxide + hydrogen (2Na + 2H₂O → 2NaOH + H₂)
Physical property of alkali metals.
Soft, low density (e.g., Li floats on water)
Group 7 name and reactivity trend.
Halogens; reactivity decreases down the group
Displacement reaction example.
Cl₂ + 2KBr → 2KCl + Br₂ (Cl displaces Br)
Physical states of halogens.
Cl₂ (gas), Br₂ (liquid), I₂ (solid)
Trend in halogen MP/BP.
Increases down the group (stronger London forces)
Rf value formula.
Rf = distance moved by substance / distance moved by solvent.
Purpose of chromatography.
Separate mixtures based on solubility in a solvent.
Why did Mendeleev leave gaps?
To predict undiscovered elements (e.g., gallium)
Why do isotopes have identical chemical properties?
Same number of electrons/protons; different neutrons affect physical properties only.
Why are Group 1 metals stored in oil?
To prevent reaction with oxygen/water
Observation when chlorine displaces bromine.
Solution turns orange (Br₂ forms).
Explain Group 7 displacement reactions.
More reactive halogens oxidize less reactive halide ions
Practical: Steps for crystallization.
- Dissolve in hot solvent. 2. Filter. 3. Evaporate. 4. Cool to crystallize
Practical: Safety with alkali metals.
Use tweezers, small pieces, wear goggles (vigorous H₂ release)
