Atomic nucleus — contents?
Protons and neutrons.
Isotopes — same?
Same element, different neutrons.
Mass number — sum?
Protons plus neutrons.
Atomic number — equals?
Number of protons.
Electron count — in a neutral atom?
Equal to protons.
Periodic table — group number?
Number of outer-shell electrons.
Electron configuration — role?
Determines an element's chemical properties.
Group 1 metals — trend?
Reactivity increases down the group.
Group 7 halogens — trend?
Reactivity decreases down the group.
Electron shell capacity — pattern?
2, 8, 8, 18, ... electrons.
Ionic compounds — definition?
Compounds formed from positive and negative ions.
Ionic formula — neutrality?
Total positive charge equals total negative charge.
Roman numeral — role?
Indicates metal's positive charge in formulas.
Balancing equations — method?
Adjust coefficients to match atom counts.
Ionic test — purpose?
Identify ions via flame colour or precipitate.
Relative atomic mass — definition?
Weighted average mass of an atom.
Molecular mass — role?
Sum of atomic masses in a molecule.
Ar calculation — isotopic abundance?
Weighted average using isotope percentages.
Mass number — protons and neutrons?
Total protons plus neutrons in nucleus.
Molecular mass — units?
Atomic mass units (amu) or unified atomic mass units.
Chemical equations — definition?
Representations of reactions with symbols and formulas.
Balancing equations — purpose?
To ensure equal atoms of each element on both sides.
Coefficients — role?
Adjust numbers to balance the equation.
Subscripts — function?
Indicate the number of atoms within a molecule.
Unbalanced equation — issue?
Atoms are not equal on both sides.
Group 1 metals — reactivity trend?
Reactivity increases down the group.
Group 7 halogens — reactivity trend?
Reactivity decreases down the group.
Group 1 metals — flame colour?
Lithium: crimson, Sodium: yellow, Potassium: lilac.
Group 7 halogens — physical states at 20°C?
Chlorine: gas, Bromine: liquid, Iodine: solid.
Displacement in Group 7 — example?
More reactive halogen displaces less reactive one, e.g., Cl2 + 2NaBr → Br2 + 2NaCl.
Ionic tests — purpose?
Identify ions via flame and precipitate tests.
Flame colours — lithium?
Crimson red flame.
Flame colours — sodium?
Yellow-orange flame.
Silver nitrate test — halides?
Precipitate forms: Cl- (white), Br- (cream), I- (yellow).
Flame test — potassium?
Lilac flame colour.
Noble gases — definition?
Inert, unreactive Group 0 elements.
Uses of helium?
Lifting gases in balloons and MRI cooling.
Noble gases — reactivity?
Very low, they rarely form compounds.
Argon — common use?
Welding inert atmosphere.
Noble gases — why inert?
Full outer electron shells prevent reactions.
Teste tes connaissances avec un QCM de 16 questions sur Introduction to Atomic and Periodic Chemistry.
1. Which statement correctly describes how reactivity changes in Group 1 metals as you move down the group?
2. What does the period number of an element tell you?
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