Periodic Table Basics
What does the atomic number of an element represent?
The number of protons in an atom.
How many electrons can the first shell hold?
2
Define atomic radius.
The distance from the nucleus to the outermost electron.
What does H₂O represent?
Water – 2 hydrogen atoms bonded to 1 oxygen atom.
What type of bond is formed between two non-metals?
Covalent bond.
Which group are the noble gases found in?
Group 18.
Write the electronic configuration of sodium (Na) using the long method.
1s² 2s² 2p⁶ 3s¹.
Which element has the highest electronegativity?
Fluorine.
Write the formula for sodium chloride.
NaCl.
Draw the Lewis structure for HCl.
H–Cl with 3 lone pairs on Cl.
Write the symbol for magnesium and state its approximate atomic mass.
Mg, atomic mass ≈ 24.
State Hund’s Rule in your own words.
Electrons fill orbitals singly before pairing up.
Explain why atomic radius decreases across a period.
Explain why atomic radius decreases across a period.
Using the table of common ions, write the formula for calcium nitrate.
Ca(NO₃)₂.
Explain why ionic bonds form between metals and non-metals.
Metals lose electrons to form cations, non-metals gain electrons to form anions, opposite charges attract.
Identify the period and group of chlorine.
Period 3, Group 17.
Draw and label the shape of a p-orbital.
Dumbbell shape (two lobes on opposite sides of nucleus).
Compare the ionisation energy of sodium and chlorine, and explain why.
Chlorine has higher ionisation energy because its electrons are held more tightly due to greater nuclear charge and smaller radius.
Deduce the formula for aluminum sulfate.
Al₂(SO₄)₃.
Draw the Lewis structure of methane (CH₄).
Carbon in the center, 4 single bonds to H atoms, no lone pairs.
Compare the properties of Group 1 (alkali metals) and Group 17 (halogens).
Group 1: highly reactive, soft metals, form +1 ions.
Group 17: highly reactive non-metals, form –1 ions, toxic in pure form.
Using Schrödinger’s method, write the electron configuration of sulfur (short method).
[Ne] 3s² 3p⁴.
Predict and justify the trend in electronegativity as you go down Group 17.
Electronegativity decreases because atomic size increases, reducing nucleus’ pull on bonding electrons.
Ammonium phosphate is a fertiliser. Write its chemical formula using ion charges.
(NH₄)₃PO₄.
Compare the structure and properties of ionic vs covalent compounds.
Ionic: lattice structure, high melting points, conduct electricity when molten/aqueous.
Covalent: molecules, low melting points, poor conductors.