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Atomic Structure and Periodic Table Chemistry
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Atomic Structure and Periodic Table Chemistry
Atomic Structure and Periodic Table Chemistry
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1
Question
What is the definition of an atom according to the AQA GCSE Chemistry content?
Answer
The smallest part of an element that can exist.
2
Question
How are atoms of elements represented chemically?
Answer
By a chemical symbol starting with a capital letter, usually one or two letters.
3
Question
What is the approximate radius of an atom and its nucleus?
Answer
Atom radius about 0.1 nm or 1 × 10^{-10} m; nucleus radius less than 1/10,000 of atom, about 1 × 10^{-14} m.
4
Question
What defines a chemical element?
Answer
A substance made up of only one type of atom.
5
Question
Why do elements on the periodic table have unique properties?
Answer
Each element consists of only one type of atom with distinct characteristics.
6
Question
What is a compound and how does it differ from elements?
Answer
A substance containing two or more different elements chemically combined in fixed proportions; unlike elements (one atom type), compounds have properties different from their elements.
7
Question
Why do compounds have different properties from their constituent elements?
Answer
Chemical combination forms new substances with altered characteristics, like iron oxide differing from iron and oxygen.
8
Question
How are compounds separated into elements?
Answer
Only by chemical reactions, not physical processes like filtration or distillation.
9
Question
What characterizes chemical reactions?
Answer
Formation of one or more new substances, often with energy change (temperature increase/decrease).
10
Question
How do you balance the symbol equation for the decomposition of water?
Answer
Start with H_2O → H_2 + O_2; count atoms (left: 2H 1O, right: 2H 2O); adjust to 2H_2O → 2H_2 + O_2 for balance (left: 4H 2O, right: 4H 2O).
11
Question
Why must symbol equations be balanced?
Answer
Same number of each atom type on reactant and product sides, conserving atoms per conservation of mass.
12
Question
List the common chemical formulas needed for balancing equations.
Answer
CO_2 (carbon dioxide), H_2O (water), O_2 (oxygen), H_2 (hydrogen), N_2 (nitrogen), NH_3 (ammonia), HCl (hydrochloric acid), H_2SO_4 (sulfuric acid).
13
Question
What are the three subatomic particles, their charges, masses, and locations?
Answer
Protons (+1, mass 1, nucleus); neutrons (0, mass 1, nucleus); electrons (-1, mass ~1/2000, shells orbiting nucleus).
14
Question
Why is almost all atomic mass in the nucleus?
Answer
Protons and neutrons have relative mass 1 each; electrons ~1/2000, negligible.
15
Question
What defines isotopes of the same element?
Answer
Same number of protons (atomic number), different number of neutrons (thus different mass numbers).
16
Question
What is an ion and how does it form?
Answer
Charged particle formed when atom/molecule gains or loses electrons; e.g., Be loses 2e^- → Be^{2+}.
17
Question
How do you fill electron shells in atoms?
Answer
Innermost first: shell 1 max 2e^-, shell 2 max 8e^-, shell 3 max 8e^-; e.g., carbon (6e): 2,4.
18
Question
What do mass number and atomic number represent on periodic table?
Answer
Atomic number: protons (electrons in neutral atom); mass number: protons + neutrons.
19
Question
How do you calculate protons, neutrons, electrons for fluorine-19 atom?
Answer
Protons: atomic #9; neutrons: 19-9=10; electrons=protons=9 (neutral).
20
Question
For Br^- ion (mass 80, atomic 35), how many protons, neutrons, electrons?
Answer
Protons 35; neutrons 80-35=45; electrons 36 (one more than protons for - charge).
21
Question
Define relative atomic mass (A_r).
Answer
Average mass of all atoms of an element compared to 1/12 mass of carbon-12 atom.
22
Question
How do you calculate relative atomic mass from isotopes?
Answer
(% isotope1 × mass1 + % isotope2 × mass2 + ...) / 100; e.g., Li: (7×6 + 93×7)/100 = 6.93.
23
Question
What is a mixture and how is it separated?
Answer
Two+ elements/compounds not chemically combined; separated by physical processes (filtration, distillation, chromatography) without new substances.
24
Question
When is filtration used and how does it work?
Answer
Separate insoluble solid (e.g., sand) from liquid (water); solid trapped in filter paper, liquid passes through to flask.
25
Question
Describe simple distillation process.
Answer
Heat solution; solvent evaporates, condenses in condenser, collects pure liquid; separates solvent from solution (e.g., water from salt).
26
Question
How does fractional distillation differ from simple distillation?
Answer
Fractionating column added; separates miscible liquids by boiling points; lowest BP evaporates first, condenses separately.
27
Question
Outline crystallization steps to separate solute from solution.
Answer
Heat evaporating basin (solvent evaporates, concentrates); cool for crystals; filter excess liquid; dry crystals.
28
Question
Why use pencil line in chromatography?
Answer
Pencil insoluble in solvents, doesn't move/interfere with spots.
29
Question
How does chromatography separate mixtures?
Answer
Solvent carries components up paper at different rates; pure substance one spot, mixture multiple.
30
Question
Summarize Dalton's atomic model.
Answer
Solid sphere; indivisible, cannot create/destroy; different spheres different elements; no subparticles.