SSC CGL Chemistry · Atomic Structure and Periodic Classification
Atoms and Elements
Element symbols and names from Latin, the heavy elements named after scientists, Dalton's atomic theory, Rutherford's gold foil, and chlorine's two isotopes.
Why this matters
Nine questions in the bank: seven from the 2023 shifts and two from the 2024 shifts. Each asks one name, number or year, so learn the two short tables.
Concept 1 of 2: Element names and symbols
Definition
Latin roots:
- Au: gold (aurum). Ag: silver (argentum). Al is aluminium, Ar argon.
- Calcium is from calx, lime.
Heavy elements:
- Mendelevium, 101, an actinide made in 1955, named after Mendeleev.
- Nobelium 102; seaborgium 106, after Glenn Seaborg.
- Plutonium, found by Seaborg in 1940: plutonium-238 heats and powers satellites.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 1 · Atomic Structure and Periodic Classification · Atoms and Elements
Au is gold, Ag is silver
Concept 2 of 2: Atomic theory and isotopes
Definition
The steps:
- John Dalton (1808): each element is made of its own unique atoms, which differ in mass; compounds form when atoms combine in simple ratios.
- Thomson found the electron (1897); Bohr gave his model in 1913.
- Rutherford fired alpha particles at gold foil about 1,000 atoms thick.
Isotopes: chlorine has two, Cl-35 (about 75.77%) and Cl-37 (about 24.23%), so its average atomic mass is about 35.5.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 2 · Atomic Structure and Periodic Classification · Atoms and Elements
Dalton, not Avogadro
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Watch out for (2)
- Au is gold, Ag is silver→ Element names and symbols
- Dalton, not Avogadro→ Atomic theory and isotopes
Test yourself on Atomic Structure and Periodic Classification
15 past SSC CGL questions from this chapter, timed at 9 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.