Periodicity Quick Kit: 18 flashcards
All 18 flashcards from this kit, free and with no sign-up.
1. State the modern periodic law.
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The physical and chemical properties of elements are a periodic function of their atomic numbers.
2. How many groups and periods are there in the modern periodic table?
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18 groups and 7 periods.
3. Define 'atomic radius'.
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The distance from the centre of the nucleus to the outermost shell containing electrons.
4. What is the trend in atomic radius across a period (left to right)?
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Atomic radius generally decreases across a period due to increase in effective nuclear charge without increase in principal quantum number.
5. What is the trend in atomic radius down a group?
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Atomic radius increases down a group because new shells are added, increasing the distance from the nucleus.
6. Define 'ionization enthalpy'.
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The minimum amount of energy required to remove the most loosely bound electron from an isolated gaseous atom in its ground state.
7. Why does ionization enthalpy generally increase across a period?
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Because effective nuclear charge increases, making it harder to remove an electron.
8. Why does ionization enthalpy generally decrease down a group?
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Because atomic size increases and the outermost electron is farther from the nucleus, experiencing more shielding.
9. Define 'electron gain enthalpy'.
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The energy change when an electron is added to a neutral gaseous atom to form a negative ion.
10. Which group has the most negative electron gain enthalpy?
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Halogens (Group 17) have the most negative electron gain enthalpy because they need one electron to achieve noble gas configuration.
11. Define 'electronegativity'.
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The tendency of an atom in a chemical compound to attract a shared pair of electrons towards itself.
12. What is the trend in electronegativity across a period and down a group?
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Electronegativity increases across a period (left to right) and decreases down a group.
13. Why do noble gases have zero electronegativity?
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Because they have stable electronic configurations and do not attract shared electrons in compounds.
14. What is the periodic trend in metallic character?
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Metallic character decreases across a period and increases down a group.
15. Which element has the highest ionization enthalpy in the periodic table?
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Helium (He) has the highest ionization enthalpy.
16. Which element has the highest electron gain enthalpy (most negative) among halogens?
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Chlorine (Cl) has the most negative electron gain enthalpy among halogens.
17. What is the anomaly of oxygen and fluorine in electron gain enthalpy?
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Oxygen and fluorine have less negative electron gain enthalpies than expected because of their small atomic size and electron-electron repulsion in the compact 2p subshell.
18. How does the size of a cation compare to its neutral atom?
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A cation is smaller than its neutral atom because it has fewer electrons and the same nuclear charge, pulling remaining electrons closer.
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