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