. He could almost see the electrons dancing around the nucleus, like the frantic commuters at New Delhi Station. He muttered to himself, "The atomic number is the number of protons... don't mix it up with mass number, Arjun. Not again." Next came the Periodic Table

: Atomic number is the count of protons in a nucleus, while mass number is the total of protons and neutrons.

Solids are primarily categorized based on the internal arrangement of their particles: States of matter: Solid, Liquid And Gas - BYJU'S

Here’s a (suitable for exams like SSC CGL, CHSL, CPO, GD, MTS, and state SSC exams).

✅ Diamond (carbon) ✅ Liquid metal at room temp: Mercury (Hg) ✅ Liquid nonmetal at room temp: Bromine (Br) ✅ Lightest gas: Hydrogen ✅ Heaviest gas (natural): Radon (Rn) ✅ Most abundant gas in air: Nitrogen (78%) ✅ Most abundant element in earth’s crust: Oxygen (46%) ✅ Noble gas used in arc welding: Argon ✅ Gas in LPG: Butane + Propane ✅ Gas in CNG: Methane ✅ Gas in fire extinguisher: CO₂

Chemistry is often considered one of the most scoring sections of the SSC (Staff Selection Commission) exams, including CGL, CHSL, MTS, and CPO. However, the vastness of the syllabus can be overwhelming. To help you navigate through the atomic structures and chemical reactions, we’ve compiled these essential SSC Chemistry notes focusing on high-yield topics. 1. Matter and Its Composition

. Memorize trends like electronegativity, atomic size, and ionization energy. Acids, Bases, and Salts

Matter is anything that has mass and occupies space. For SSC exams, focus on the physical and chemical classifications.