Periodic Trends
What is atomic radius?
The distance from the nucleus to the outermost electron shell of an atom.
What are protons, neutrons, and electrons?
Protons (+) and neutrons (0) are in the nucleus; electrons (–) orbit the nucleus.
What is ionic bonding?
A bond formed by the transfer of electrons between metals and non-metals.
State of ionic compounds at room temperature?
Solid.
Which has a higher electronegativity: Fluorine or Oxygen?
Fluorine – it's the most electronegative element.
Why does atomic radius decrease across a period?
Because more protons are added to the nucleus, pulling electrons closer without adding shells.
Where are electrons located?
In energy levels or shells surrounding the nucleus.
What is covalent bonding?
A bond formed by sharing electrons between two non-metals.
Why are metals malleable?
Layers of atoms can slide over each other while delocalised electrons hold the structure.
Explain why sodium (Na) has a low ionisation energy.
It has one valence electron that is far from the nucleus and easily removed.
What is electronegativity?
The ability of an atom to attract electrons in a chemical bond.
What is the mass number?
The total number of protons and neutrons in the nucleus.
What is metallic bonding?
Positive metal ions surrounded by a ‘sea’ of delocalised electrons.
Why are covalent molecular substances poor conductors?
They have no free-moving charged particles.
Draw a dot diagram for H₂O.
Two hydrogen atoms each share one electron with oxygen, which has two lone pairs.
Why does ionisation energy increase across a period?
More protons attract electrons more strongly, requiring more energy to remove an electron.
How do isotopes differ?
They have the same number of protons but different numbers of neutrons.
Why do ionic compounds conduct electricity when molten?
The ions are free to move and carry charge when the lattice breaks down.
Why do covalent network solids have high melting points?
Strong covalent bonds extend throughout the structure, requiring lots of energy to break.
Explain why graphite conducts electricity.
Graphite has delocalised electrons between its layers that can move and carry current.
Compare group 1 and group 17 elements in terms of reactivity.
Group 1 elements lose electrons easily; Group 17 gain electrons easily—both are very reactive.
Explain how ions form in terms of electron gain/loss.
Atoms lose or gain electrons to achieve a full outer shell, forming positive or negative ions.
Compare properties of ionic and covalent substances.
Ionic: high melting point, conducts when molten. Covalent: low melting point, doesn’t conduct.
Predict properties of silicon dioxide based on its bonding.
High melting point, hard, doesn’t conduct – due to strong covalent network structure.
Predict the melting point trend across Period 3 (Na to Cl).
t increases then decreases – metals have higher melting points; non-metals (like Cl₂) are low.