: Physical combinations of substances without a fixed ratio.
Number of protons in the nucleus of an atom.
Proposed by Henry Moseley . It organizes elements by increasing atomic number . It consists of 7 Periods (horizontal rows) and 18 Groups (vertical columns). Periodic Trends (Left to Right vs. Top to Bottom) Across a Period (Left to Right) Down a Group (Top to Bottom) Atomic Radius Decreases (due to increased nuclear charge) Increases (due to addition of new shells) Ionization Energy Increases (harder to lose electrons) Decreases (easier to lose electrons) Electron Affinity Electronegativity Increases (Fluorine is the most electronegative) Metallic Character 4. Chemical Bonding and Radioactivity
Practice at least the last 5 years' papers to understand the pattern. chemistry notes ssc
Radioactivity is the spontaneous disintegration of unstable atomic nuclei, discovered by . Marie and Pierre Curie discovered Radium and Polonium. Alpha ( ) Particles: Helium nuclei (
(an allotrope of carbon) is the hardest naturally occurring substance known. Metalloids
). They have high melting points and conduct electricity in molten or aqueous states. : Physical combinations of substances without a fixed ratio
: The total number of protons and neutrons combined.
Matter is anything that has mass and occupies space. It is classified physically and chemically. Physical Classification
Substances formed when two or more elements chemically combine in a fixed ratio (e.g., Pure Water ( H2Ocap H sub 2 cap O ), Carbon Dioxide ( CO2cap C cap O sub 2 It organizes elements by increasing atomic number
) are soft metals that can be cut with a knife. They are stored in kerosene because they react violently with air and water. Non-Metals Brittle, poor conductors of heat and electricity.
Designed by Henry Moseley . It is based on atomic numbers . It contains 18 vertical groups and 7 horizontal periods . Periodic Trends (Left to Right vs. Top to Bottom)
Atoms of different elements with the same mass number but different atomic numbers (e.g., Argon and Calcium, both having mass number 40).
Contain single bonds between carbon atoms. General formula: CnH2n+2cap C sub n cap H sub 2 n plus 2 end-sub (e.g., Methane - CH4cap C cap H sub 4 , Ethane - C2H6cap C sub 2 cap H sub 6 Unsaturated Hydrocarbons: Alkenes: Contain at least one double bond. General formula: CnH2ncap C sub n cap H sub 2 n end-sub (e.g., Ethene - C2H4cap C sub 2 cap H sub 4 Alkynes: Contain at least one triple bond. General formula: CnH2n−2cap C sub n cap H sub 2 n minus 2 end-sub (e.g., Ethyne/Acetylene - C2H2cap C sub 2 cap H sub 2 8. Chemical Formulas and Common Names (High-Yield for SSC)
Hexagonal layered structure. Good conductor due to free electrons. Used as a lubricant and in pencils.