Periodic Trends Flashcards: Atomic Radius, Ionization Energy & Electronegativity
Review 88 concise cards on atomic and ionic radius, shielding, effective nuclear charge, ionization energy, electron affinity, electronegativity, metallic character, exceptions, and comparisons.
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Periodic Trends Flashcards: Atomic Radius, Ionization Energy & Electronegativity
Study the core periodic trends with 88 independently written English flashcards for high-school and introductory-college chemistry. The deck separates broad patterns from the reasons behind them and uses generally where real configurations create exceptions.
What the cards practice
The sequence covers four useful recall paths: term to definition; table movement to a general property direction; cause to effect through shell number, shielding, distance, and effective nuclear charge; and a concrete pair or isoelectronic set to the expected comparison. Atomic and ionic radius, first and successive ionization energies, electron affinity, electronegativity, metallic character, and selected reactivity links are all included.
The course-level exceptions are deliberately small: Be versus B, Mg versus Al, N versus O, P versus S, and Cl versus F electron affinity. Electron-affinity wording distinguishes a favorable electron gain from the sign convention used by a source. Electronegativity stays tied to bonded atoms, and ionic-radius comparisons state when an isoelectronic rule applies.
Learning order
Definitions and table structure come first. General directions follow, then causal models, ion-size rules, successive-ionization reasoning, limited exceptions, and applied comparisons. Related prompts are spaced apart in a fixed order; the review scheduler handles longer-term interleaving after installation.
Scope
This deck teaches qualitative periodic-trend reasoning. It excludes exact numerical property tables, memorizing values for all 118 elements, advanced transition-metal irregularities, diagonal relationships, melting and boiling trends, broad group trivia, and copied examination or competitor material. It supports chemistry practice but does not replace calculation, laboratory, or full-course problem solving.
Sources and license
Core trends and explanations were checked against OpenStax Chemistry: Atoms First 2e, section 3.5 and its electronegativity discussion in section 4.2. Terminology was cross-checked against the IUPAC Gold Book entries for ionization energy, electron affinity, and electronegativity.
The prompts, answers, examples, organization, metadata, and generated cover were created independently from common chemistry knowledge and original work. No protected cards, textbook prose, source figures, exact property tables, logos, or third-party media were copied.
The Common knowledge · CC0 1.0 label applies only to the original prompts, answers, examples, organization, metadata, and cover, to the extent applicable rights exist. It does not claim ownership of scientific facts or third-party material.
Source review date: August 29, 2026.
Kadi za fungu hili
Kadi namba 1
Swali
What is a periodic trend?
Jibu
A recurring pattern in element properties as atomic number increases across periods and down groups.
Kadi namba 2
Swali
What does covalent radius measure?
Jibu
Half the distance between the nuclei of two identical atoms joined by a covalent bond.
Kadi namba 3
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What is first ionization energy?
Jibu
The minimum energy needed to remove the most loosely bound electron from an isolated gaseous atom in its ground state.
Kadi namba 4
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What is electronegativity?
Jibu
An atom's ability to attract shared electrons toward itself in a chemical bond.
Kadi namba 5
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What is a period on the periodic table?
Jibu
A horizontal row. For main-group elements, moving across a period fills orbitals in the same principal electron shell.
Kadi namba 6
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What is ionic radius?
Jibu
A measure of an ion's size, usually inferred from distances between ions in crystals.
Kadi namba 7
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What does electron affinity describe?
Jibu
The energy change when an electron is added to an isolated gaseous atom to form a gaseous anion.
Kadi namba 8
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What does metallic character describe?
Jibu
How readily an element shows metallic behavior, especially losing valence electrons and forming cations.
Kadi namba 9
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What is a group on the periodic table?
Jibu
A vertical column. Main-group elements in one group usually share a valence-electron pattern and similar chemistry.
Kadi namba 10
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What is effective nuclear charge?
Jibu
The net positive pull an electron feels from the nucleus after shielding and electron–electron repulsion are taken into account.
Kadi namba 11
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What are successive ionization energies?
Jibu
The energies needed to remove electrons one after another from the same atom, then from its increasingly positive ions.
Kadi namba 12
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How does electronegativity difference relate to bond polarity?
Jibu
A larger difference generally produces a more uneven electron distribution and a more polar bond.
Kadi namba 13
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Why do main-group elements in one group often behave similarly?
Jibu
They have the same general number and arrangement of valence electrons, which drive much of their bonding and reactivity.
Kadi namba 14
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What is electron shielding?
Jibu
The reduction in nuclear attraction felt by an electron because other electrons lie between it and the nucleus and repel it.
Kadi namba 15
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Why does the definition of ionization energy specify a gaseous atom?
Jibu
It isolates the atom from bonding and intermolecular effects, so the energy reflects electron removal from that species itself.
Kadi namba 16
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Where are metals and nonmetals generally found on the periodic table?
Jibu
Metals occupy the left and center; nonmetals cluster toward the upper right, with metalloids near the boundary.
Kadi namba 17
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What changes in the electron arrangement across a main-group period?
Jibu
Electrons are added to the same principal shell while the nucleus gains one proton from one element to the next.
Kadi namba 18
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How does atomic radius generally change from left to right across a period?
Jibu
It decreases.
Kadi namba 19
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How does first ionization energy generally change from left to right across a period?
Jibu
It increases, although a few recurring subshell and electron-pairing exceptions interrupt the rise.
Kadi namba 20
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How does electronegativity generally change from left to right across a period?
Jibu
It increases for the elements normally assigned electronegativity values.
Kadi namba 21
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What changes in the electron arrangement down a main-group group?
Jibu
Each step adds a higher principal electron shell while preserving a similar valence-electron pattern.
Kadi namba 22
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How does atomic radius generally change down a group?
Jibu
It increases.
Kadi namba 23
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How does first ionization energy generally change down a group?
Jibu
It decreases.
Kadi namba 24
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How does electronegativity generally change down a group?
Jibu
It decreases.
Kadi namba 25
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How does effective nuclear charge generally change across a main-group period?
Jibu
It increases because nuclear charge rises while added electrons enter the same principal shell and do not fully shield one another.
Kadi namba 26
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How does a cation's radius compare with its neutral parent atom?
Jibu
The cation is smaller.
Kadi namba 27
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How does electron addition generally change across a period?
Jibu
It generally becomes more energetically favorable toward the right, but electron affinity has substantial exceptions and depends on the sign convention used.
Kadi namba 28
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How does metallic character generally change from left to right across a period?
Jibu
It decreases.
Kadi namba 29
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Why are valence electrons generally farther from the nucleus down a group?
Jibu
They occupy shells with higher principal quantum numbers, so the electron cloud extends farther outward.
Kadi namba 30
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How does an anion's radius compare with its neutral parent atom?
Jibu
The anion is larger.
Kadi namba 31
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How does favorable electron addition generally change down a group?
Jibu
It generally becomes less favorable as the added electron enters a larger, more shielded shell, though electron-affinity irregularities are common.
Kadi namba 32
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How does metallic character generally change down a group?
Jibu
It increases.
Kadi namba 33
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Why does shielding change less than nuclear charge across a main-group period?
Jibu
The added electrons enter the same principal shell, so they do not shield one another as effectively as inner-shell electrons do.
Kadi namba 34
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Which has the larger atomic radius, Li or Na?
Jibu
Na. It lies below Li and has an additional occupied electron shell.
Kadi namba 35
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Which has the larger atomic radius, Na or Mg?
Jibu
Na. Atomic radius generally decreases from left to right across Period 3.
Kadi namba 36
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How does greater electron–nucleus distance affect electrostatic attraction?
Jibu
It weakens the attraction, all else being equal.
Kadi namba 37
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How do successive ionization energies for one element compare?
Jibu
Each successive ionization energy is higher than the one before it because an electron is removed from an increasingly positive species.
Kadi namba 38
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Which has the higher first ionization energy, Li or Na?
Jibu
Li. Its valence electron is closer to the nucleus and less shielded.
Kadi namba 39
Swali
Which has the higher first ionization energy, Na or Mg?
Jibu
Mg. Its greater effective nuclear charge holds the valence electrons more tightly.
Kadi namba 40
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Why does forming a cation usually shrink an atom?
Jibu
Electron loss reduces electron–electron repulsion and increases the nuclear pull per remaining electron; losing the outer shell can shrink it sharply.
Kadi namba 41
Swali
Which element is most electronegative on the Pauling scale?
Jibu
Fluorine.
Kadi namba 42
Swali
Which is more electronegative, Li or Na?
Jibu
Li. Electronegativity generally decreases down Group 1.
Kadi namba 43
Swali
Which is more electronegative, Na or Mg?
Jibu
Mg. Electronegativity generally increases across Period 3.
Kadi namba 44
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What does a large jump between successive ionization energies reveal?
Jibu
The next electron would come from a lower, core shell; the number removed before the jump indicates the valence-electron count for a main-group atom.
Kadi namba 45
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Why is Cl⁻ larger than neutral Cl?
Jibu
The added electron increases repulsion within the valence shell while the nuclear charge stays the same.
Kadi namba 46
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How do you compare the radii of isoelectronic species?
Jibu
The species with more protons is smaller because the same number of electrons feels a stronger nuclear attraction.
Kadi namba 47
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Why does an atom have no single sharp physical radius?
Jibu
Its electron cloud has no hard edge, so atomic size depends on a defined measurement such as covalent, metallic, or van der Waals radius.
Kadi namba 48
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Why are noble-gas electronegativities often omitted in introductory tables?
Jibu
Electronegativity describes attraction in a bond, and many noble gases form too few ordinary bonds for a standard value to be useful on common scales.
Kadi namba 49
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Why does forming an anion usually expand an atom?
Jibu
The extra electron increases electron–electron repulsion and lowers the nuclear pull available per electron.
Kadi namba 50
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Order O²⁻, F⁻, and Ne from largest to smallest radius.
Jibu
O²⁻ > F⁻ > Ne. All have 10 electrons, and increasing proton count pulls that electron cloud inward.
Kadi namba 51
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After which removal does Na show its first large ionization-energy jump?
Jibu
After the first electron. Removing one valence electron leaves a stable core, so the second removal reaches that core.
Kadi namba 52
Swali
Does electronegativity difference create a universal ionic-versus-covalent cutoff?
Jibu
No. A larger difference usually means more bond polarity, but bonding lies on a continuum and context matters.
Kadi namba 53
Swali
How do noble gases generally differ from halogens in electron affinity?
Jibu
Adding an electron to a noble gas is generally unfavorable because it must begin a higher-energy shell; halogens usually gain one much more favorably.
Kadi namba 54
Swali
Which is smaller, Na⁺ or Mg²⁺?
Jibu
Mg²⁺. Both have 10 electrons, but Mg²⁺ has one more proton.
Kadi namba 55
Swali
After which removal does Mg show its first large ionization-energy jump?
Jibu
After the second electron. Mg has two valence electrons, so the third removal reaches a core shell.
Kadi namba 56
Swali
How does electronegativity differ from electron affinity?
Jibu
Electronegativity is a relative measure of attraction for shared electrons in a bond; electron affinity is an energy change for adding an electron to an isolated gaseous species.
Kadi namba 57
Swali
How are atomic radius and first ionization energy generally related?
Jibu
A larger radius usually means a lower first ionization energy because the valence electron is farther from the nucleus and easier to remove.
Kadi namba 58
Swali
Which has the more exothermic first electron affinity, F or Cl?
Jibu
Cl. Fluorine's very compact 2p shell creates stronger electron–electron repulsion for the incoming electron, so this pair breaks the simple down-group expectation.
Kadi namba 59
Swali
Which has the higher first ionization energy, Be or B?
Jibu
Be. B loses a higher-energy 2p electron, while Be loses a more penetrating 2s electron from a filled 2s subshell.
Kadi namba 60
Swali
Why does Group 1 metal reactivity generally increase down the group?
Jibu
The valence electron is farther out and more shielded, so its first ionization energy falls and electron loss becomes easier.
Kadi namba 61
Swali
How are atomic radius and electronegativity generally related?
Jibu
Smaller atoms usually attract bonding electrons more strongly, so electronegativity tends to rise as radius falls.
Kadi namba 62
Swali
Why is Na⁺ much smaller than neutral Na?
Jibu
Na loses its entire third-shell valence level, leaving the smaller neon-like electron configuration.
Kadi namba 63
Swali
Which has the higher first ionization energy, Mg or Al?
Jibu
Mg. Al's removed electron is a higher-energy 3p electron, while Mg loses a more penetrating 3s electron from a filled 3s subshell.
Kadi namba 64
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Why does halogen reactivity generally decrease down Group 17?
Jibu
Larger radius and greater shielding weaken attraction for an incoming electron, so oxidizing ability generally falls. Particular reactions still depend on bond energies and conditions.
Kadi namba 65
Swali
Why do Groups 2 and 15 often interrupt the simple electron-affinity trend?
Jibu
Group 2 has a filled s subshell and Group 15 has a half-filled p subshell, so an added electron enters a less favorable arrangement.
Kadi namba 66
Swali
Can ion charge alone rank two unrelated ionic radii?
Jibu
No. Shell number, electron count, proton count, oxidation state, and crystal environment can all matter; the isoelectronic rule needs the same electron count.
Kadi namba 67
Swali
Which has the higher first ionization energy, N or O?
Jibu
N. Its half-filled 2p subshell is relatively stable; O has one paired 2p orbital, and repulsion makes one electron easier to remove.
Kadi namba 68
Swali
In which direction does nonmetallic character generally increase?
Jibu
Up and to the right, opposite the general trend in metallic character.
Kadi namba 69
Swali
Within the same principal shell, which penetrates closer to the nucleus: an s or p orbital?
Jibu
An s orbital. Greater penetration means its electrons are less shielded and usually lower in energy than p electrons in the same shell.
Kadi namba 70
Swali
How do same-charge ion radii generally change down a group?
Jibu
They increase as occupied electron shells are added.
Kadi namba 71
Swali
Which has the higher first ionization energy, P or S?
Jibu
P. Its half-filled 3p subshell is relatively stable; S contains a paired 3p orbital that increases repulsion and eases removal.
Kadi namba 72
Swali
Why should simple periodic-direction rules be used cautiously for transition metals?
Jibu
d-electron filling, shielding, oxidation state, and contraction effects make their property changes less regular than main-group trends.
Kadi namba 73
Swali
Why do periodic-trend statements usually say “generally”?
Jibu
Subshell energies, electron pairing, radius definitions, and element-specific configurations create real exceptions to the broad patterns.
Kadi namba 74
Swali
Which has the larger atomic radius, K or Br?
Jibu
K. Both are in Period 4, and atomic radius generally decreases from left to right.
Kadi namba 75
Swali
Which has the higher first ionization energy, Mg or Cl?
Jibu
Cl. Its valence electrons experience greater effective nuclear charge and are held more tightly.
Kadi namba 76
Swali
Which is more electronegative, Al or Si?
Jibu
Si. Electronegativity generally increases across Period 3.
Kadi namba 77
Swali
Which has the larger atomic radius, O or F?
Jibu
O. Atomic radius generally decreases across Period 2.
Kadi namba 78
Swali
Which has the higher first ionization energy, K or Br?
Jibu
Br. First ionization energy generally increases across Period 4.
Kadi namba 79
Swali
Which is more electronegative, Mg or Cl?
Jibu
Cl. It lies farther right in Period 3.
Kadi namba 80
Swali
Which has the larger atomic radius, Al or Si?
Jibu
Al. Atomic radius generally decreases across Period 3 as effective nuclear charge rises.
Kadi namba 81
Swali
Which has the higher first ionization energy, O or F?
Jibu
F. This pair follows the general increase across Period 2.
Kadi namba 82
Swali
Which is more electronegative, K or Br?
Jibu
Br. Electronegativity generally increases across Period 4.
Kadi namba 83
Swali
Which has the larger atomic radius, Mg or Cl?
Jibu
Mg. Both are in Period 3, and Mg lies farther left.
Kadi namba 84
Swali
Which has the higher first ionization energy, Al or Si?
Jibu
Si. This pair follows the general increase across Period 3.
Kadi namba 85
Swali
Which is more electronegative, O or F?
Jibu
F, the most electronegative element on the Pauling scale.
Kadi namba 86
Swali
Order Al³⁺, Mg²⁺, Na⁺, Ne, F⁻, and O²⁻ from smallest to largest radius.
Jibu
Al³⁺ < Mg²⁺ < Na⁺ < Ne < F⁻ < O²⁻. All have 10 electrons, so radius grows as proton count falls.
Kadi namba 87
Swali
Why do upper-right nonmetals usually hold valence electrons tightly?
Jibu
Their relatively small radii and high effective nuclear charges create strong attraction between the nucleus and valence electrons.
Kadi namba 88
Swali
Across a main-group period, what shared cause links smaller radius, higher ionization energy, and higher electronegativity?
Jibu
Increasing effective nuclear charge pulls the same-shell valence electrons inward and holds them more strongly.
kadi 88
Periodic Trends Flashcards: Atomic Radius, Ionization Energy & Electronegativity
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