Periodic Classification of Elements — Karnataka (SSLC) Class 10 Science Solutions (Free)
Free step-by-step Karnataka (SSLC) Class 10 Science solutions for "Periodic Classification of Elements" — important questions with detailed answers, download PDF for board exam preparation.
TL;DR: Free step-by-step Karnataka (SSLC) Class 10 Science solutions for "Periodic Classification of Elements" — important questions with detailed answers, d…
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Q1: What is the periodic table? Why was it necessary to classify elements?
Periodic table = systematic arrangement of elements by atomic number in rows (periods) and columns (groups). Necessity: 1) Over 100 elements exist; classification helps organize and predict properties. 2) Elements in same group (vertical column) have similar chemical properties due to same valence electrons. 3) Helps predict reactivity, electronegativity, formation of compounds. Mendeleev left gaps for undiscovered elements, predicting their properties accurately.
Q2: What is the relationship between atomic number, number of electrons, and position in periodic table?
Atomic number = number of protons = number of electrons (in neutral atom). Position: Group number = number of valence electrons (rightmost column with H). Period number = number of electron shells. Example: Na (Z=11): electron config 2,8,1; period 3 (3 shells), group 1 (1 valence electron). This arrangement explains why elements in same group react similarly; valence electrons determine bonding.
Q3: Classify elements into metals, non-metals, and metalloids. Give examples of each.
Metals: left side of periodic table, shiny, conduct electricity, form cations (Na, Fe, Cu, Al). Non-metals: right side, dull, poor conductors, form anions or share electrons (C, O, N, S, Cl). Metalloids: along diagonal between metals and non-metals, intermediate properties (B, Si, As, Sb). Metals are most abundant; non-metals essential for life (C, N, O); metalloids used in semiconductors (Si in computers).
Q4: What are valence electrons? Why do elements in same group have similar properties?
Valence electrons = outermost electrons in electron shell; determine chemical behavior and bonding. Elements in same group (vertical column) have same number of valence electrons: Group 1 has 1 (alkali metals), Group 17 has 7 (halogens), Group 18 has 8 (noble gases, inert). Same valence electrons = similar reactivity and similar compound formation. Example: Li, Na, K all have 1 valence electron, all react with water forming hydroxide.
Q5: What are periodic trends? Explain electronegativity and ionization energy trends.
Periodic trends = properties change systematically across period or down a group. Electronegativity (tendency to attract electrons): increases left-to-right across period, decreases down a group (F highest at 4.0, Cs lowest at 0.79). Ionization energy (energy to remove electron): increases left-to-right, decreases down group. Reason: nuclear charge increases left-to-right, atomic radius increases down group. These trends help predict reactivity and bonding type.
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