🧪 Atomic Structure & Chemical Formula - Class 7 Slay Sheet 💅

Definitions

1. 💖 What’s a Chemical Formula?

It's like a tiny recipe that shows what atoms are in a compound and how many. Examples: H₂O = 2 Hydrogen besties + 1 Oxygen queen CO₂ = 1 Carbon + 2 Oxygen baddies

2. 🧠 Structure of an Atom (but make it cute)

Atoms are the main characters, and they come with: Proton (+1) → center stage (nucleus) Neutron (0) → neutral vibes, also in nucleus Electron (–1) → zooming around in shells

Shell Vibes (Max Electrons):

K-shell: 2 L-shell: 8 M-shell: 18

3. 🧃Why Do Elements React?

They’re trying to live their best life = become stable. So they gain, lose, or share electrons to fill their outer shell. That’s how chemical friendships (aka compounds) happen 💅

4. ✨ Examples of Iconic Element Collabs:

H₂ + O₂ → H₂O (WATER) Na + Cl → NaCl (SALT) C + O₂ → CO₂ (breathable slay)

5. 💥 Valency = Element’s Collab Energy

Valency tells how many electrons an atom wants to gain/lose/share. Popular Valency Levels: 1: H, Na, Cl (basic but slay) 2: O, Mg, Ca (stable queens) 3: Al, N (chaotic good) 4: C, Si (main characters)

✍️ Writing Formulas with Valency (Like a Pro):

Steps:

Write the symbols
Write valencies below
Criss-cross the valencies
Subscript them = final slay formula

Examples:

Na (1) + Cl (1) → NaCl (classic)
Al (3) + O (2) → Al₂O₃ (power combo)

🌈 Periodic Table: Your Elemental BFF Chart

Sorted by how many protons (atomic number).

Groups (vertical) = similar vibes

Periods (horizontal) = more shells, more drama

Group Tea:

Group 1 = Drama queens (super reactive metals)
Group 17 = Shady non-metals (Cl is THAT girl)
Group 18 = Chill squad (noble gases = no drama)

Layout:

Metals on the left (strong, silent types)
Non-metals on the right (emotional intellectuals)

Why Atoms Form Compounds

Atoms form compounds to achieve a more stable electron configuration. This usually involves achieving a full valence shell similar to that of the noble gases. Atoms can share (covalent bonding), transfer (ionic bonding), or pool (metallic bonding) electrons to achieve this stability.

Valency and Its Types

Valency describes how atoms combine with each other. It is related to the number of electrons an atom needs to gain, lose, or share to achieve a full outer shell. For example, oxygen with a valency of 2 needs two electrons to complete its valence shell, so it often forms compounds like water (H₂O).

Writing Chemical Formulas Using Valency

To write chemical formulas, one must understand the valency of each participating element. For instance, in sodium chloride (NaCl), sodium (Na) has a valency of +1, and chlorine (Cl) has a valency of -1. The formula is balanced when the total positive charge equals the total negative charge.

The Periodic Table: A Gen-Z Approach

Think of the periodic table as the ultimate 'Posse of Elements' where each column (group) shares similar 'attitudes' (chemical properties). The table helps in predicting how different elements will interact and the types of bonds they will form.

To remember :

💡 Fun Facts You Should Flex:

Noble gases = too cool to react
Electrons always fill low shells first (lazy tbh)
Compounds have fixed formulas — no freelancing here 😌