11 min readConcept sheetSection A MCQ (1 mark) and objective (2 marks, two parts, often match a type with its group); Section B short answer (3 marks) or long answer (5 marks): types of elements and their positions

Types of elements and where they sit: main group, transition, inner transition and noble gases; metals, non-metals and metalloids

Main group elements fill groups 1, 2 and 13 to 17, noble gases group 18, and transition elements groups 3 to 12. Metals sit left, non-metals right, metalloids between.

Main group (normal) elementsGroups 1, 2 and 13 to 17; the outermost shell is incomplete (fewer than 8 electrons)

Transition elementsGroups 3 to 12; all metals with variable valency; the two outermost shells are incomplete

Inner transition elementsLanthanoids (Z = 58 to 71) and actinoids (Z = 90 to 103), printed in two rows below the table

MetalloidsShow properties of both metals and non-metals; lie along a zigzag line from boron (group 13) down to polonium (group 16)

Kinds of elements in the long form table

Type	Where	Outer shells	Key features
Main group (normal or representative)	Groups 1, 2 and 13 to 17	Outermost shell incomplete	Include the most reactive metals and non-metals
Noble gases	Group 18	Outer shell full: 8 electrons (helium 2)	Valency 0, almost unreactive, all gases
Transition elements	Groups 3 to 12, the middle block	Two outermost shells incomplete	All metals; high melting and boiling points; good conductors; variable valency; many are catalysts; some are magnetic (iron, cobalt, nickel)
Inner transition elements	Lanthanoids (58 to 71) in period 6 and actinoids (90 to 103) in period 7, printed below	Three outermost shells incomplete	Placed with lanthanum (57) and actinium (89) in group 3

Metals, non-metals and metalloids

Metals are on the left and in the middle. Group 1 holds the alkali metals (Li, Na, K, Rb, Cs, Fr). Group 2 holds the alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra).
Non-metals are on the right. Group 17 holds the halogens (F, Cl, Br, I, At), and group 16 the chalcogens (O, S, Se, Te, Po).
Metalloids show properties of both. They lie along a zigzag line from boron (group 13) down to polonium (group 16): boron, silicon, germanium, arsenic, antimony, tellurium and polonium.
Hydrogen sits in group 1 but is a non-metal gas.

Where the names come from

Transition means change. These metals form a bridge between the strongly metallic elements on the left and the non-metals on the right. The noble gases are named because they rarely combine with anything, just as gold, a 'noble' metal, does not tarnish. The lanthanoids are named after lanthanum, and the actinoids after actinium, the element just before each series.

Activity: name the element and place it (puzzle)

Unscramble each word to find an element. Then write its group and period in the modern table.

1
GORNTEIN: a gas that makes up most of the air.
Answer: nitrogen, 2, 5, so group 15, period 2.
2
MUDSIO: a soft metal kept under kerosene.
Answer: sodium, 2, 8, 1, so group 1, period 3.
3
RLHINCOE: a gas used to clean drinking water.
Answer: chlorine, 2, 8, 7, so group 17, period 3.
4
LIONSIC: the metalloid in computer chips and solar cells.
Answer: silicon, 2, 8, 4, so group 14, period 3.
5
MILEHU: the light gas in party balloons.
Answer: helium, 2, so group 18, period 1.
6★
Check each answer with its configuration: the number of shells gives the period.

★ key step

Activity: explore the modern periodic table (online lab)

Open an interactive periodic table in an online lab or an app.

1
Click any element and note its atomic number, group and period.
2
Turn on the colour key for metals, non-metals and metalloids. Find the zigzag line of metalloids.
3
Pick group 1 and read the configurations from top to bottom.
Observe: one valence electron each, and one more shell at each step.
4
Pick period 3 and read across.
Observe: the valence electrons rise from 1 to 8.
5★
Find the lanthanoids and actinoids, and see where they really belong: group 3.

★ key step

In real life

Transition metals work as catalysts in Indian industry: iron helps make ammonia for fertiliser, and nickel helps turn vegetable oil into vanaspati ghee.

Exam angle

1 marks: “In which group of the modern periodic table are the halogens placed?” Group 17.

3 marks: “Where are (a) noble gases, (b) transition elements and (c) metalloids placed in the modern periodic table? Give one property of each.” (a) Group 18; valency 0 and almost unreactive. (b) Groups 3 to 12; metals with variable valency. (c) Along the zigzag line from boron to polonium; they show both metallic and non-metallic properties.

2 marks: “What are inner transition elements? Why are they printed below the main table?” The lanthanoids (58 to 71) and actinoids (90 to 103), whose three outermost shells are incomplete. They belong in group 3 of periods 6 and 7, but are printed separately for convenience, to keep the table compact.

Remember it

Left metals, right non-metals, zigzag metalloids. Groups 1, 2 and 13 to 17 main; 3 to 12 transition; 18 noble.