Grade 10 chemisty – Periodicity Quiz
1. What does 'periodicity' in the periodic table mean?
Periodicity refers to recurring trends (like atomic size, ionization energy, electronegativity) that repeat across periods as atomic number increases.
2. What does the atomic number of an element represent?
Atomic number equals the number of protons and defines the identity of an element on the periodic table.
3. How does atomic radius change when moving left to right across a period?
Across a period protons increase, increasing pull on electrons and reducing atomic size despite electrons being added to the same shell.
4. How does atomic radius change down a group (column) in the periodic table?
Going down a group, each element has an extra occupied energy level, making atoms larger despite increased nuclear charge.
5. Which trend best describes first ionisation energy across a period from left to right?
As nuclear charge increases across a period, it becomes harder to remove an electron, so ionisation energy rises (with a few small exceptions).
6. How does first ionisation energy change down a group?
Additional shells increase distance and shielding, making it easier to remove an outer electron; ionisation energy falls down a group.
7. Which of these elements is most electronegative?
Electronegativity increases across a period and decreases down a group; fluorine (top right area) is the most electronegative element.
8. What is the common charge of ions formed by Group 1 (alkali) metals?
Alkali metals have one valence electron which they lose easily to achieve a noble-gas configuration, forming +1 ions.
9. When sodium metal reacts with water, which products are formed?
Sodium + water → sodium hydroxide (a strong base) + hydrogen gas. This is why care is needed when handling alkali metals.
10. Why are noble gases generally unreactive (inert)?
Full valence shells mean noble gases do not need to gain, lose or share electrons, so they show very little chemical reactivity.
11. What does the period number (row) tell you about an element?
Elements in period 3 have three electron shells, period number equals the principal energy level of valence electrons.
12. Elements in the same group have similar chemical properties because they have the same:
Valence electrons determine bonding and reactivity; elements in a group share the same valence electron count and so behave similarly.
13. Which element is most metallic: lithium, beryllium, boron or carbon?
Metallic character decreases across a period. Lithium, at the left, shows the most metallic properties (conductivity, malleability) among these.
14. Which of the following elements commonly forms a +2 ion?
Calcium (Group 2) has two valence electrons which it loses to form a stable +2 ion; sodium forms +1, chlorine forms -1, neon is inert.
15. Why does atomic radius generally increase down a group despite increased nuclear charge?
Each step down a group adds a shell; increased distance and shielding mean outer electrons are further out despite more protons.
16. Which of these trends are both generally true when going across a period from left to right?
Across a period atoms hold electrons more tightly (higher ionisation) and so show less metallic behaviour (less likely to lose electrons).
17. Which element among the following has the largest atomic radius: sodium (Na), magnesium (Mg), aluminium (Al), silicon (Si)?
Atomic radius decreases across a period; sodium is furthest left among these, so it has the largest radius.
18. Which element is likely to form a negative ion (anion) with a -1 charge?
Chlorine (group 17) needs one electron to complete its valence shell, so it commonly gains one electron to form Cl-.
19. What is the main reason for the irregularity where boron has a lower first ionisation energy than beryllium?
Sub-shell structure causes small exceptions: the 2p electron in boron is higher in energy and less tightly held than beryllium’s paired 2s electrons.
20. Which statement explains the shielding effect?
Electrons in inner shells block some nuclear attraction, so outer electrons feel less pull and are easier to remove (lower ionisation).
21. Which element has a full valence shell and is therefore most chemically inert among these: oxygen, fluorine, neon, sodium?
Neon is a noble gas with a full outer shell, making it very unreactive compared to the other elements listed.
22. What is the definition of first ionisation energy?
First ionisation energy measures how strongly an atom holds its outermost electron and is measured for gas-phase atoms.
23. Which statement explains why alkali metals are very reactive?
Alkali metals have one loosely held outer electron, so they readily lose it to form positive ions and react vigorously, especially with water.
24. Why do elements in the same period show a change from metallic to non-metallic character?
Across a period atoms add protons and electrons in the same shell; increasing nuclear attraction leads to less tendency to lose electrons, so metallic character decreases.
25. Which pair of elements are in the same group and therefore have similar reactivity: magnesium and calcium, carbon and oxygen, sodium and chlorine, helium and lithium?
Magnesium and calcium are both in Group 2 (alkaline earth metals) and share similar properties like forming +2 ions and comparable reactivity patterns.
26. Which property generally increases across a period and is associated with an atom's ability to attract electrons in a bond?
Electronegativity rises across a period because atoms more strongly attract electrons as nuclear charge grows and radius shrinks.