Megik Science Academy

23/08/2026

23/08/2026

highlights

23/08/2026

Electron affinity (energy released gaining an electron):

➡️ Across a period = INCREASES ⬇️ Down a group = DECREASES

Halogens have the highest — they're one electron away from a full shell.

Bonus: Diagonal Relationships

Li ↔ Mg Be ↔ Al B ↔ Si

These pairs behave alike chemically, despite being in different groups — because of similar atomic size and charge density.

(CTA): That's the periodic table in a thread 🧪

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23/08/2026

It also has FAMILIES with special names:

Group 1 = Alkali metals (super reactive) Group 2 = Alkaline earth metals Group 17 = Halogens Group 18 = Noble gases (unreactive)
Now the trends 👇

Atomic size: ➡️ Across a period = DECREASES ⬇️ Down a group = INCREASES

Why? More protons pull electrons in tighter across a period. New shells push electrons out down a group.

Ionization energy (energy to remove an electron):

➡️ Across a period = INCREASES ⬇️ Down a group = DECREASES

Smaller atoms hold their electrons tighter → harder to remove.

23/08/2026

Why does atomic size DECREASE as you move across the periodic table, but INCREASE as you move down?

A simple thread to help you master Periodic Trends for WAEC/NECO Chemistry 🧵👇
First, the Periodic Law:

"Properties of elements are periodic functions of their atomic number."

Arranged by Moseley (1913) using atomic number — not atomic mass like Mendeleev originally used.
The table has 4 BLOCKS based on electron sub-shells:

s-block: Groups 1-2 p-block → Groups 13-18 d-block ; Groups 3-12 (transition metals) f-block : bottom two rows.
Get more, just comment NOTES to get the free E-notes or WhatsApp: 08125415442 or
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