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Atomic Structure and Periodic Trends
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1
Question
What are the three primary subatomic particles in atoms and where are they located?
Answer
Protons and neutrons in the nucleus; electrons orbit around the nucleus.
2
Question
What is the charge, mass, and symbol of a neutron?
Answer
Charge 0, mass ~1 amu, symbol n0.
3
Question
What is the charge, mass, and symbol of an electron?
Answer
Charge -1, mass ~1/1840 amu, symbol e-.
4
Question
Why is atomic mass not a whole number for most elements?
Answer
Weighted average of naturally occurring isotopes.
5
Question
How is the number of electrons in a neutral atom determined?
Answer
Equal to the number of protons.
6
Question
How do you calculate neutrons from mass number and atomic number?
Answer
Neutrons = mass number − atomic number.
7
Question
What is an isotope?
Answer
Atoms of the same element with different mass numbers.
8
Question
How is isotopic notation written for Carbon-14?
Answer
¹⁴C (atomic number 6, mass 14).
9
Question
What are cations and anions?
Answer
Cations are positively charged ions; anions are negatively charged ions.
10
Question
What did Dalton contribute to atomic theory?
Answer
First atomic theory proposing atoms are indivisible and combine in ratios.
11
Question
What did Millikan measure in 1916?
Answer
Electron charge (and mass ~9.11×10⁻²⁸ g).
12
Question
What did Rutherford's gold foil experiment reveal about the nucleus?
Answer
Nucleus is small, dense, positively charged; atoms are mostly empty space.
13
Question
What is the Bohr model's key idea about electron arrangement?
Answer
Electrons orbit nucleus in discrete energy levels.
14
Question
What does the quantum mechanical model say about electron positions?
Answer
Electrons exist in probability clouds rather than fixed orbits.
15
Question
What is the Periodic Law as reorganized by Moseley?
Answer
Elements ordered by atomic number show periodic properties.
16
Question
What is atomic radius and how does it trend across a period?
Answer
Distance from nucleus to outer electrons; decreases across a period.
17
Question
What is effective nuclear charge (Z_eff)?
Answer
Net positive charge experienced by an electron; increases across a period.
18
Question
What is ionization energy?
Answer
Energy required to remove an electron from an atom.
19
Question
How does ionization energy trend down a group and across a period?
Answer
Decreases down a group; increases across a period.
20
Question
What is metallic character and its trend across a period?
Answer
Tendency to lose electrons; decreases across a period.
21
Question
What is electronegativity?
Answer
Attraction of an atom for shared electrons in a bond.
22
Question
What is the general trend of electronegativity in the periodic table?
Answer
Increases across a period; decreases down a group.
23
Question
Which element is the most electronegative and why?
Answer
Fluorine; small size and high nuclear charge.
24
Question
How do ionic radii change when atoms form cations and anions?
Answer
Cations smaller; anions larger than neutral atoms.
25
Question
What is the basic composition of atoms?
Answer
Protons, neutrons, and electrons.
26
Question
Who developed the first comprehensive periodic table and what was unique about it?
Answer
Mendeleev; left gaps for undiscovered elements.
27
Question
What did Dobereiner contribute to early periodic classification?
Answer
Triads of similar elements.
28
Question
What did Newlands propose with the Law of Octaves?
Answer
Elements in order of atomic mass showed repeating properties.
29
Question
What is the key takeaway from Rutherford's nuclear model?
Answer
Nucleus is dense and positive; atom mostly empty space.
30
Question
What was the core idea of Bohr's energy levels?
Answer
Electrons occupy discrete shells; transitions emit/absorb energy.