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.
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Kort 1
Fråga
What is a periodic trend?
Svar
A recurring pattern in element properties as atomic number increases across periods and down groups.
Kort 2
Fråga
What does covalent radius measure?
Svar
Half the distance between the nuclei of two identical atoms joined by a covalent bond.
Kort 3
Fråga
What is first ionization energy?
Svar
The minimum energy needed to remove the most loosely bound electron from an isolated gaseous atom in its ground state.
Kort 4
Fråga
What is electronegativity?
Svar
An atom's ability to attract shared electrons toward itself in a chemical bond.
Kort 5
Fråga
What is a period on the periodic table?
Svar
A horizontal row. For main-group elements, moving across a period fills orbitals in the same principal electron shell.
Kort 6
Fråga
What is ionic radius?
Svar
A measure of an ion's size, usually inferred from distances between ions in crystals.
Kort 7
Fråga
What does electron affinity describe?
Svar
The energy change when an electron is added to an isolated gaseous atom to form a gaseous anion.
Kort 8
Fråga
What does metallic character describe?
Svar
How readily an element shows metallic behavior, especially losing valence electrons and forming cations.
Kort 9
Fråga
What is a group on the periodic table?
Svar
A vertical column. Main-group elements in one group usually share a valence-electron pattern and similar chemistry.
Kort 10
Fråga
What is effective nuclear charge?
Svar
The net positive pull an electron feels from the nucleus after shielding and electron–electron repulsion are taken into account.
Kort 11
Fråga
What are successive ionization energies?
Svar
The energies needed to remove electrons one after another from the same atom, then from its increasingly positive ions.
Kort 12
Fråga
How does electronegativity difference relate to bond polarity?
Svar
A larger difference generally produces a more uneven electron distribution and a more polar bond.
Kort 13
Fråga
Why do main-group elements in one group often behave similarly?
Svar
They have the same general number and arrangement of valence electrons, which drive much of their bonding and reactivity.
Kort 14
Fråga
What is electron shielding?
Svar
The reduction in nuclear attraction felt by an electron because other electrons lie between it and the nucleus and repel it.
Kort 15
Fråga
Why does the definition of ionization energy specify a gaseous atom?
Svar
It isolates the atom from bonding and intermolecular effects, so the energy reflects electron removal from that species itself.
Kort 16
Fråga
Where are metals and nonmetals generally found on the periodic table?
Svar
Metals occupy the left and center; nonmetals cluster toward the upper right, with metalloids near the boundary.
Kort 17
Fråga
What changes in the electron arrangement across a main-group period?
Svar
Electrons are added to the same principal shell while the nucleus gains one proton from one element to the next.
Kort 18
Fråga
How does atomic radius generally change from left to right across a period?
Svar
It decreases.
Kort 19
Fråga
How does first ionization energy generally change from left to right across a period?
Svar
It increases, although a few recurring subshell and electron-pairing exceptions interrupt the rise.
Kort 20
Fråga
How does electronegativity generally change from left to right across a period?
Svar
It increases for the elements normally assigned electronegativity values.
Kort 21
Fråga
What changes in the electron arrangement down a main-group group?
Svar
Each step adds a higher principal electron shell while preserving a similar valence-electron pattern.
Kort 22
Fråga
How does atomic radius generally change down a group?
Svar
It increases.
Kort 23
Fråga
How does first ionization energy generally change down a group?
Svar
It decreases.
Kort 24
Fråga
How does electronegativity generally change down a group?
Svar
It decreases.
Kort 25
Fråga
How does effective nuclear charge generally change across a main-group period?
Svar
It increases because nuclear charge rises while added electrons enter the same principal shell and do not fully shield one another.
Kort 26
Fråga
How does a cation's radius compare with its neutral parent atom?
Svar
The cation is smaller.
Kort 27
Fråga
How does electron addition generally change across a period?
Svar
It generally becomes more energetically favorable toward the right, but electron affinity has substantial exceptions and depends on the sign convention used.
Kort 28
Fråga
How does metallic character generally change from left to right across a period?
Svar
It decreases.
Kort 29
Fråga
Why are valence electrons generally farther from the nucleus down a group?
Svar
They occupy shells with higher principal quantum numbers, so the electron cloud extends farther outward.
Kort 30
Fråga
How does an anion's radius compare with its neutral parent atom?
Svar
The anion is larger.
Kort 31
Fråga
How does favorable electron addition generally change down a group?
Svar
It generally becomes less favorable as the added electron enters a larger, more shielded shell, though electron-affinity irregularities are common.
Kort 32
Fråga
How does metallic character generally change down a group?
Svar
It increases.
Kort 33
Fråga
Why does shielding change less than nuclear charge across a main-group period?
Svar
The added electrons enter the same principal shell, so they do not shield one another as effectively as inner-shell electrons do.
Kort 34
Fråga
Which has the larger atomic radius, Li or Na?
Svar
Na. It lies below Li and has an additional occupied electron shell.
Kort 35
Fråga
Which has the larger atomic radius, Na or Mg?
Svar
Na. Atomic radius generally decreases from left to right across Period 3.
Kort 36
Fråga
How does greater electron–nucleus distance affect electrostatic attraction?
Svar
It weakens the attraction, all else being equal.
Kort 37
Fråga
How do successive ionization energies for one element compare?
Svar
Each successive ionization energy is higher than the one before it because an electron is removed from an increasingly positive species.
Kort 38
Fråga
Which has the higher first ionization energy, Li or Na?
Svar
Li. Its valence electron is closer to the nucleus and less shielded.
Kort 39
Fråga
Which has the higher first ionization energy, Na or Mg?
Svar
Mg. Its greater effective nuclear charge holds the valence electrons more tightly.
Kort 40
Fråga
Why does forming a cation usually shrink an atom?
Svar
Electron loss reduces electron–electron repulsion and increases the nuclear pull per remaining electron; losing the outer shell can shrink it sharply.
Kort 41
Fråga
Which element is most electronegative on the Pauling scale?
Svar
Fluorine.
Kort 42
Fråga
Which is more electronegative, Li or Na?
Svar
Li. Electronegativity generally decreases down Group 1.
Kort 43
Fråga
Which is more electronegative, Na or Mg?
Svar
Mg. Electronegativity generally increases across Period 3.
Kort 44
Fråga
What does a large jump between successive ionization energies reveal?
Svar
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.
Kort 45
Fråga
Why is Cl⁻ larger than neutral Cl?
Svar
The added electron increases repulsion within the valence shell while the nuclear charge stays the same.
Kort 46
Fråga
How do you compare the radii of isoelectronic species?
Svar
The species with more protons is smaller because the same number of electrons feels a stronger nuclear attraction.
Kort 47
Fråga
Why does an atom have no single sharp physical radius?
Svar
Its electron cloud has no hard edge, so atomic size depends on a defined measurement such as covalent, metallic, or van der Waals radius.
Kort 48
Fråga
Why are noble-gas electronegativities often omitted in introductory tables?
Svar
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.
Kort 49
Fråga
Why does forming an anion usually expand an atom?
Svar
The extra electron increases electron–electron repulsion and lowers the nuclear pull available per electron.
Kort 50
Fråga
Order O²⁻, F⁻, and Ne from largest to smallest radius.
Svar
O²⁻ > F⁻ > Ne. All have 10 electrons, and increasing proton count pulls that electron cloud inward.
Kort 51
Fråga
After which removal does Na show its first large ionization-energy jump?
Svar
After the first electron. Removing one valence electron leaves a stable core, so the second removal reaches that core.
Kort 52
Fråga
Does electronegativity difference create a universal ionic-versus-covalent cutoff?
Svar
No. A larger difference usually means more bond polarity, but bonding lies on a continuum and context matters.
Kort 53
Fråga
How do noble gases generally differ from halogens in electron affinity?
Svar
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.
Kort 54
Fråga
Which is smaller, Na⁺ or Mg²⁺?
Svar
Mg²⁺. Both have 10 electrons, but Mg²⁺ has one more proton.
Kort 55
Fråga
After which removal does Mg show its first large ionization-energy jump?
Svar
After the second electron. Mg has two valence electrons, so the third removal reaches a core shell.
Kort 56
Fråga
How does electronegativity differ from electron affinity?
Svar
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.
Kort 57
Fråga
How are atomic radius and first ionization energy generally related?
Svar
A larger radius usually means a lower first ionization energy because the valence electron is farther from the nucleus and easier to remove.
Kort 58
Fråga
Which has the more exothermic first electron affinity, F or Cl?
Svar
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.
Kort 59
Fråga
Which has the higher first ionization energy, Be or B?
Svar
Be. B loses a higher-energy 2p electron, while Be loses a more penetrating 2s electron from a filled 2s subshell.
Kort 60
Fråga
Why does Group 1 metal reactivity generally increase down the group?
Svar
The valence electron is farther out and more shielded, so its first ionization energy falls and electron loss becomes easier.
Kort 61
Fråga
How are atomic radius and electronegativity generally related?
Svar
Smaller atoms usually attract bonding electrons more strongly, so electronegativity tends to rise as radius falls.
Kort 62
Fråga
Why is Na⁺ much smaller than neutral Na?
Svar
Na loses its entire third-shell valence level, leaving the smaller neon-like electron configuration.
Kort 63
Fråga
Which has the higher first ionization energy, Mg or Al?
Svar
Mg. Al's removed electron is a higher-energy 3p electron, while Mg loses a more penetrating 3s electron from a filled 3s subshell.
Kort 64
Fråga
Why does halogen reactivity generally decrease down Group 17?
Svar
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.
Kort 65
Fråga
Why do Groups 2 and 15 often interrupt the simple electron-affinity trend?
Svar
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.
Kort 66
Fråga
Can ion charge alone rank two unrelated ionic radii?
Svar
No. Shell number, electron count, proton count, oxidation state, and crystal environment can all matter; the isoelectronic rule needs the same electron count.
Kort 67
Fråga
Which has the higher first ionization energy, N or O?
Svar
N. Its half-filled 2p subshell is relatively stable; O has one paired 2p orbital, and repulsion makes one electron easier to remove.
Kort 68
Fråga
In which direction does nonmetallic character generally increase?
Svar
Up and to the right, opposite the general trend in metallic character.
Kort 69
Fråga
Within the same principal shell, which penetrates closer to the nucleus: an s or p orbital?
Svar
An s orbital. Greater penetration means its electrons are less shielded and usually lower in energy than p electrons in the same shell.
Kort 70
Fråga
How do same-charge ion radii generally change down a group?
Svar
They increase as occupied electron shells are added.
Kort 71
Fråga
Which has the higher first ionization energy, P or S?
Svar
P. Its half-filled 3p subshell is relatively stable; S contains a paired 3p orbital that increases repulsion and eases removal.
Kort 72
Fråga
Why should simple periodic-direction rules be used cautiously for transition metals?
Svar
d-electron filling, shielding, oxidation state, and contraction effects make their property changes less regular than main-group trends.
Kort 73
Fråga
Why do periodic-trend statements usually say “generally”?
Svar
Subshell energies, electron pairing, radius definitions, and element-specific configurations create real exceptions to the broad patterns.
Kort 74
Fråga
Which has the larger atomic radius, K or Br?
Svar
K. Both are in Period 4, and atomic radius generally decreases from left to right.
Kort 75
Fråga
Which has the higher first ionization energy, Mg or Cl?
Svar
Cl. Its valence electrons experience greater effective nuclear charge and are held more tightly.
Kort 76
Fråga
Which is more electronegative, Al or Si?
Svar
Si. Electronegativity generally increases across Period 3.
Kort 77
Fråga
Which has the larger atomic radius, O or F?
Svar
O. Atomic radius generally decreases across Period 2.
Kort 78
Fråga
Which has the higher first ionization energy, K or Br?
Svar
Br. First ionization energy generally increases across Period 4.
Kort 79
Fråga
Which is more electronegative, Mg or Cl?
Svar
Cl. It lies farther right in Period 3.
Kort 80
Fråga
Which has the larger atomic radius, Al or Si?
Svar
Al. Atomic radius generally decreases across Period 3 as effective nuclear charge rises.
Kort 81
Fråga
Which has the higher first ionization energy, O or F?
Svar
F. This pair follows the general increase across Period 2.
Kort 82
Fråga
Which is more electronegative, K or Br?
Svar
Br. Electronegativity generally increases across Period 4.
Kort 83
Fråga
Which has the larger atomic radius, Mg or Cl?
Svar
Mg. Both are in Period 3, and Mg lies farther left.
Kort 84
Fråga
Which has the higher first ionization energy, Al or Si?
Svar
Si. This pair follows the general increase across Period 3.
Kort 85
Fråga
Which is more electronegative, O or F?
Svar
F, the most electronegative element on the Pauling scale.
Kort 86
Fråga
Order Al³⁺, Mg²⁺, Na⁺, Ne, F⁻, and O²⁻ from smallest to largest radius.
Svar
Al³⁺ < Mg²⁺ < Na⁺ < Ne < F⁻ < O²⁻. All have 10 electrons, so radius grows as proton count falls.
Kort 87
Fråga
Why do upper-right nonmetals usually hold valence electrons tightly?
Svar
Their relatively small radii and high effective nuclear charges create strong attraction between the nucleus and valence electrons.
Kort 88
Fråga
Across a main-group period, what shared cause links smaller radius, higher ionization energy, and higher electronegativity?
Svar
Increasing effective nuclear charge pulls the same-shell valence electrons inward and holds them more strongly.
88 kort
Periodic Trends Flashcards: Atomic Radius, Ionization Energy & Electronegativity
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